
That would be pretty awesome (nice screenshots btw). SSB Retro would be a great downloadable title to drum up excitement for the release of the next proper series installment.
As for the future of the series, I think it'd be great if they included plenty of non-Nintendo characters, though I do think they would have had to appear on a Nintendo console at some point (sorry, Master Chief). I'd like to see Saki from Sin and Punishment as a playable character instead of just an assist trophy, and putting in Bayonetta would be a great way to promote her new game coming to the Wii U.