I seriously can't wait for the games, I'm getting the PSP just for BBS. As for 358/2, I'm gonna play it on my friend's DS. Lastly the mobile one, I'm not sure if I'm getting it.
KH : BBS - Ten years from the original KH. A better improved version of the original battle system, from the screens I saw. Mickey probably wasn't a king then.
KH : 358/2 - Roxas' days in Organization XIII. Wi-Fi is official. You get to choose to play as any of the Organization's mambers.
KH : Mobile - Explains better of the timeline. Not much is known -_-'
Basically, I will play both of the games. I check all KH fansites everyday for release dates, so I can tell you guys.