I'm not sure if this is already implemented, but judging by the duels that I've tried so far, I think it isn't.
This idea is pretty much derived from Atlantica Online, a turn-based mmo:
I suggest that in duels, a battle timer will be given to each player. During his turn, he will be given 30 seconds to make his move. This is to prevent players from hogging duels if they are lagging/dcing, and also provide a challenge to players because they will need to use the set amount of time to react.
(Think about it, if you were dueling in real life and your pokemon doesn't receive a command, it will just get wacked by your opponent lol!)
A time bar will be provided so that the player can gauge how long he has left, for example:
[url=http://s224.photobucket.com/user/shoptrader20/media/suggestion1_zps788c51a2.jpg.html][/URL]
The time bar will gradually decrease (as if poisoned by 1 hp/sec), and if no move is made within the 30 seconds limit, the pokemon will automatically use the first move on its list.
What do you guys reckon about it?