Honestly think we might hear something at Nintendo's E3 or something, it really is only a matter of time. Also they'll probably need one soon to accomodate for the inevitable fact that Sonic will be in Smash 5 lol.
I don't think it necessarily has to be something big though.
I think a Switch-tailor-made Sonic game that actually uses the Switch's capabilities, but GOOD would be very ideal.
You've got a variety of tools at hand; the Joy-Cons, their gyro, motion, HD Rumble, and even the IR camera could all be used in creative ways. They just need someone with real vision and creativity to pull it off, or else risk having another Sonic Lost World where the Wii U's features were just very "throw shit on the wall and see what sticks" with little to no thought put into them. They also came down to where they thought "can they" instead of "should they". The features used for the Wisps were so bad they had to patch in button controls for most of them after release.
Honestly I think Yuji Naka would've been absolutely the man for the job. It's sad he's at Square Enix now, making it even more unlikely he'll ever work on Sonic ever again. At least at Prope he could've done so. Hell Prope was founded with partial funding by Sega and was initially partnered with them on Let's Tap and Let's Catch.
Arzest would be the other ideal dev with their very close ties to Nintendo and also co-headed by Naoto Ohshima, who many seem to forget he wasn't just Sonic's co-creator and main character designer, but directed hits such as Sonic CD, NiGHTS into Dreams, and Burning Rangers.
An Arzest-developed Sonic game with Nintendo backing it has been a dream of mine. Closest was literally Mario & Sonic Rio 2016 3DS which was co-developed by Arzest with Spike Chunsoft.
No time like the present.