I've seen a lot of people be intimidated by the new gen, some of them even saying they'd leave since there would be a ton of additional grind either due to their comps becoming useless or because of new comps creeping up the place. However in a lot of cases some older comps will still be pretty viable in their tiers and some might only need a minor change to remain viable. Others however will need re-eving or even re-breeding. With this guide I plan to list all the changes the new gen will bring to most Pokemon. Keep in mind Hidden Abilities might not be added on the same patch as gen5 so don't invest on breeders for something that relies on its hidden ability yet.
Notable gen 4 Pokemon added in Platinum
The placements mentioned below are just my personal opinion of where I think they'll end up, it has nothing to do with TC decisions and it's mostly speculation.
-Abomasnow-
Its Grass/Ice typing is awkward due to its number of weaknesses and its slow, mixed attacking stat spread certainly doesn't salvage it, but it has a solid movepool and an surprisingly effective STAB combination that can blindside a lot of team builders. Snow Warning also lets it chip away at almost everything and allows it to use Blizzard without worrying about missing.
-Drapion-
A strangely bulky and fast Poison/Dark Pokemon, has 95 base speed 70/110/75 bulk and a solid 90 atk which can be boosted through Swords Dance. It also has access to Toxic Spikes, Taunt and Whirlwind.
-Empoleon
With an incredible Water/Steel typing, Empoleon has a solid stat spread that not only does it let it tank a good amount of hits, but it can sometimes function as a makeshift offensive mon. Its better use is as a hazard control pokemon with access to both Defog and Stealth Rock, sadly its downfall comes in its lack of reliable recovery. It's the type of mon that may enjoy a brief stay in OU before dropping to UU.
-Garchomp-
One of the most controversial Pokemon in the history of the game. With a stat spread that's downright sublime, this Dragon/Ground Pokemon has been banned numerous times in Smogon's OU in gen 4 and gen 5 due to how good it was, yes that's with all legendaries included. 102 base speed is its most notable asset, letting it outpace a large amount of the metagame, including the normally considered great base 100s, a 130 base attack which can be boosted to obscene levels with Swords Dance, and bulk rivaling Swampert (If Swampert only invested in speed and atk, but you get the idea) and a useable enough spatk to run mixed sets to break past defensive walls. Not to mention its Sand Veil ability granting it a chance to avoid attacks in the sand. Personally I expect this Pokemon to be pretty much the best mon in the game, even with the minor nerfs to Base Powers, there's very little that can stop this beast, I predict OU or in the worst case Uber.
-Gastrodon-
Basically a different take on Quagsire. Water/Ground. Storm Drain grants it an immunity to Water moves and lets it raise its spatk when hit by them. Another difference is it's slightly bulkier on the specially defensive side and frailer in the physically defensive side than quag, Moveset wise they are also pretty similar. Not sure where it'll end up, probably UU but it may sometimes take a trip to OU.
-Infernape-
A really versatile mixed attacking Fire/Fighting mon with lots of utility options, with a great speed tier in 108 base speed and solid 104 offensive stats, as well as access to a myriad of great moves such as Stealth Rock, Taunt, Fake out, U-turn, Swords Dance, Mach Punch, Flare Blitz, Close Combat, Nasty Plot, Flamethrower(duh), Focus Blast, Grass Knot, Slack off, Will-o-wisp, etc, there's no end to the stuff you can do with this mon. Not really set in stone but expect it to be OU.
-Rampardos-
A monotype Rock type mon with an obscene 165 base attack, Head Smash and solid ability in Mold Breaker. While its speed is terrible It could be a fearsome asset with Rock Polish or under Trick Room.
-Rotom-
A fairly unique Pokemon who can change forms depending of the house appliance it possesses. Each has a different typing, learn a different move according to their typing and with the exception of its base form, the same stat spread. Its shared notable moves are Volt Switch, Pain Split, Will-O-Wisp, Thunder Wave, Trick, Foul Play, Discharge, Shadow Ball, Thunderbolt, Reflect and Light Screen.
Base form: Electric/Ghost - 50/50/77/95/77/91
Usually ran as an offensive choice attacker, there's nothing much to say, it has decent stats and a unique typing that may help you hard counter the common Togekiss sets.
All appliance forms: 50/65/107/105/107/86
Wash Form: Electric/Water
I like to describe this as the love child between a Weezing and a Lanturn, because that's what it is, Lanturn's typing and Weezing's everything else. Will-O-Wisp, Pain Split, Levitate with a single weakness, an electric move, ring any bells yet?
Historically Rotom-W has been OU, and insanely good in it as an anti metagame pick that kills all fun. Our version however will destroy fun even more with access to Defog which it recently acquired in USUM so brace yourselves because I expect this to be the most used mon in OU (Sadly for me). It is normally run as a defensive pivot like Weezing was, bulky ev spread, don't let that deter you from using more offensive variants though, they are quite good. Its unique move is Hydro Pump
Heat form: Electric/Fire
Normally used more as an offensive pivot rather than a defensive one due to its Stealth Rock weakness (Despite its large amount of resistences). Very few Pokemon can take hits from its STAB combination too, so it makes for a premium specs user. Rotom-H has normally gravitated around UU its whole life, I don't expect that to be an exception here. Its unique move is Overheat.
Mow form: Electric/Grass
Probably the best of the "bad" forms, like Rotom-H, Rotom-C is usually ran as an offensive Pokemon, at this point the descriptions are kind of redundant and the last two forms are more or less the same. Its unique move is Leaf Storm.
Frost form: Electric/Ice
Electric/Ice is a neat offensive typing, sadly ice is not so much defensively, STAB Boltbeam is pretty good though, well Blizzard rather than beam since that's its unique move.
Fan form. Electric/Flying
Equipped with an Air Balloon it gains a terrifying triple immunity to Ground type attacks, and that's the only somewhat unique thing about it, probably the worst form, gains access to Air Slash and a somewhat solid typing, that's only brought down by its redundant ability but it can make do as a fighting type check I guess, not a big fan tbh.
-Spiritomb-
Dark/Ghost, meaning no weaknesses, fairly solid and balanced stats and movepool, abyssmal speed but 108 defenses and 92 offenses. Its movepool consists of your standard Ghost type stuff.
-Staraptor-
A mon cursed to be BL in every single generation it has been in, and for good reason, Flying/Normal with base 100 speed, 120 attack and Intimidate, fairly similar to Dodrio, this mon has access to Close Combat instead of Jump Kick as well as the powerhouse moves Brave Bird and Double Edge, priority in Quick Attack and unlike Dodrio access to U-Turn.
Pursuit, Final Gambit and Roost are also notable options as well for it.
Without Zapdos, numerous base 100+ speed mons and Thundurus around, will Staraptor make it to OU on its own merit? Will the geniuses who manipulate the flow of the MMO UU metagame find a way to deal with this bird there if it doesn't quite make the cut? Only time will tell.
-Toxicroak-
Useable both in rain and against it, with Dry Skin granting it a Scald immunity as well as some additional recovery in the rain, this Poison/Fighting pokemon has access to a myriad of set up options with Bulk Up, Nasty Plot and Swords Dance as well as a versatile enough offensive movepool such as Thunder and Ice Punch, Drain Punch, Sucker Punch, Vacuum Wave, Sludge Bomb/Wave, Focus Blast and Focus Punch. With rain's popularity in OU I expect it to end up there as both an asset and a counter to it.
Changes to already existing Pokemon
Misdreavus/Mismagius/Yamask/Cofagrigus: They all gain Nasty Plot through breeding with Spiritomb.
Under the spoiler is the old post, made originally when MMO only covered gen 3 and was about to gain access to Unova. If you're completely unfamiliar with anything past gen3 give it a read, the tiers are all outdated and a lot of predictions regarding the metagame and updates are/were wrong (Such as HAs coming soon), but overall it should tell you what each newer mon does and what newer things already existing mons got. I was going to chisel at it and fix the images, tiers and some of the wronger things but the forums tab had a stroke mid edit and all the progress was lost, so screw it.
