Interesting article over at SimHQ on the inroads mobile gaming is making and its impact on PC and console gaming.
http://simhq.com/_mobile/mobile_007a.html (http://simhq.com/_mobile/mobile_007a.html)
I like to think that it isn't taking over, but expanding gaming itself. There are a ton of uses for tablets and smartphones that can play into how players get involved with their games. There's a Conflict of Heroes app for tracking rounds, victory points and CAPs, and if you have Smartglass for Xbox use, you can get some game-centric use (minimap, stats, etc).
I doubt tablets will ever beat the raw power of a PC, but they've certainly reached the point to handle some wargames with relative ease.