Ladies and gentlemen, we are in a Sonic Renaissance

I heard about that!
I'm so excited for Sonic Adventure 3 to come out, although it won't be exactly titled "Sonic Adventure 3"
They're gonna come up with a different name, although it'll still be considered an Adventure game
They're doing this in order for the game to appeal to older Sonic fans that have played or greatly familiar with the Adventure games, and newer Sonic fans that have just joined the franchise from the movies and don't know of the Adventure games...

When's it coming out?

I don't know...
The president of SEGA did mention something about another Sonic Adventure game coming out back in 2016, and here we are 6 years later with him actually saying that it WILL come out

Hoping soon

same
It'll probably take at least a year

To drop a teaser. I would hope it would take at least 3 years to give the devs time