IMO the battle system doesn't need changing, it's the rest of the 'cookie cutter'. I'm talking about things like gyms, team ..., the elite four, etc. I would far prefer the 6th gen to shake them up rather than the battle system (I haven't really been keeping up with B/W, so as far as I know they could have change some of those).
The simplistic battle system is what make pokemon so attractive, everybody understands it. At the same time, Pokemon is also the more 'hardcore' RPG I've ever played, due to IVs, EVs, etc.