Yeah, people in 7DS can still battle for PE2K. There is a sign up thread on PE2K for people wanting a chance to be in the war...It's stickied in the PE2K battle forums.
And about joining Desu...It's possible...I know I won't join Team Storm. They are pretty weak in my opinion. I battled some of their higher ups already, and beat them every time. The one battle I honestly should have lost, the guy showed pitty on me...(I was up, 4-2...Then I got flinchhaxed twice in a row by a Waterfall...Should have been hi win, 2-0...but he pretty much let me win, 1-0). That's kinda weak too, really. I wouldn't have showed mercy like that.
Team Dark looked good, at first, but it seems mostly inactive there. My options are narrowing...ALOT!