That doesn't mean anything, the likelihood is that Sumo is working with a number of publishers including Sega and Konami. But like i said Sumo isn't working on Mario kart vs Sonic, its more likely to be how they did it in SSB having a guest appearence in the next Mario kart, made by Nintendo.
I don't get what you mean.
There's no clue they aren't making another ASR(S0L even asked around on SEGA forums & SSMB for advice). I don't think Sumo has the manpower to work on 2 games at one, so goin off that, and their name on the PS4 dev list, they can't be makin the game the TC was thinkin happened. IIRC Sumo wanted Kirby in Transformed and couldn't get him for pretty much the reason I posted(see also, Link & Samus in Ultimate Alliance)
Maybe they're working on another ASR-esque racer from another publisher, but since they're pretty much SEGA's go to racing devs, I doubt it.