Sonic 2017's Official Title is Sonic Forces, Sonic Mania Delayed to Summer

SEGA announced a pair of updates regarding the two Sonic the Hedgehog games the publisher has in development.
The first gameplay of modern Sonic in Sonic Forces is coming soon.

SONIC MANIA Delayed Until Summer 2017 — GameTyrant

Sonic Fans Club

Sega came up with a way to get fans excited about Sonic the Hedgehog again

2017 – A Year In Supersonic Review

Sega Delays Sonic Mania, Reveals Official Title for Sonic 2017 - mxdwn Games

Sonic Mania Delayed To Summer - Fans Told It Takes Time

My Nintendo in North America Adds New Sonic Rewards

Sonic Mania

Sonic Fans Club

Sonic Superstars Confirms 60 FPS on Switch : r/NintendoSwitch

Sonic Fans Club

sonic mania News, Rumors and Information - Bleeding Cool News Page 1

Sega publishes first gameplay footage of Sonic Forces, delays retro-inspired Sonic Mania

Sonic Mania Hit With Delay As Sonic Forces Gets Official Reveal - SlashGear

Dr. Robotnik – Wizard Dojo