they had the invitational in the nokia theater this year anyway, so it probably wouldn't be so strange.
given the success of treehouse live and the general format, i don't see them returning to a press conference. i would be kind of disappointed if they did- this was a good first step, and i would love to see how they would expand on it in future years.
something i noted last year that struck me as odd was that for all of microsoft and sony having better infrastructure with their online, they seem really behind the times when it comes to engaging their fans. nintendo's had a couple of years now to work out what makes a 'nintendo direct' and this year especially it seems that they're making these things more and more interesting. i wonder if they will take a page out of sony's book and show these in select theaters next year.
i was impressed they didn't get stuck revealing the quality of life platform, and surprised they stuck to showing off mostly wii u games from first-party developers (aside from hyrule warriors and bayonetta). they even kept actual game announcements in codename steam, mario party 10, mario vs donkey kong, and star fox for after the show. i think those could have been in there and time could have been cut on the yoshi's woolly world and splatoon segments.
most of all, i like how this makes e3 into an actual three-day event. it was always cool to see the press conferences, and then details about games on day one, but the show kind of lost its appeal by day two, and nobody cared anymore on day three. now it feels like there's an actual convention going on for a couple of days- and gives more of a sense that e3 isn't just a couple hours in a room for a couple of companies.