Sonic Mania 2 was never in the works because Sega and its devs

The next 2D Sonic has “that old classic Sonic feel” but needed a “current look”.

Sonic Mania 2, Video Game Fanon Wiki

Sonic Mania Review!, Even though I was born in 1999, the cl…

Sonic Mania review - Polygon

Sonic Mania 2 was never in the works because Sega and its devs wanted to move away from pixel art and “make something fresh”

Because of how superior fan-made Sonic games are to the official ones from SEGA, is SEGA deliberately tasking Sonic fans with saving Sonic the Hedgehog in their stead? - Quora

Sega just ensured that I won't be playing Sonic Origins

Sonic Superstars Developers Explain Why They're Finally Abandoning Green Hill Zone - IGN

Sonic Origins Dev 'Very Unhappy' With SEGA Over His Part Of The Game

Sonic Mania's sequel was never developed due to Sega's concerns over the size of its audience

SONIC MANIA Developer Interview! Working with Sonic Team, Stardust Speedway and More — E3 2017

Why Sonic Mania 2 didn't come out : r/SonicTheHedgehog

SEGA will be looking at the reception of Sonic Mania to determine the direction of the series : r/Games

Review - Sonic Origins - WayTooManyGames

Sonic Mania is a nostalgic reminder of the series' core issues