Well here we are: another Worlds Unite teaser. It's not just classic Mega Man this time -- look, there's X! And, and... oh dear. Sonic Boom's Sticks the Badger.
So yeah, further confirmation Worlds Unite is a four-way-crossover with classic, X, Archie's traditional Sonic series and Sonic Boom. It'll be interesting to see how this pans out, for better or worse.
See the full teaser image at IGN UK. Sonic and Mega Man: Worlds Unite story arc kicks off Spring 2015.
Source: IGN UK