I don't know how much further you can take that franchise. Ultimate seems like the limit. What else can be done besides add more fighters, stages, power ups etc?
Maybe take into 3D like Power Stone? That might work and would be a massive change for the series.
If we get a Direct this month it'll have to be on the 12th or 19th (13th/20th in Japan) so it wouldn't interfere with Pokemon Day on Feb. 27th. The past several February Directs (maybe Directs in general?) have been on Wednesday in the US/Thursday in Japan.