usually, I would just go "Utter bullc**p! SEGA wouldn't risk defiling the most popular 2 games in Sonic's 3D career!" but, with the lowering popularity of the two adventure titles, they wouldn't have to worry about that. However, I still think this is wrong. 1, with modern gameplay, why make the game the sequel to a game that used the Classic 3D formula? Also, with most people thinking SA2 is overrated and just generally bad, why would they make a sequel to it? With Sonic 2006, the gameplay was still popular, but dear lord, that game was the last nail in the coffin for the franchise at the time, so the series needed a mild reboot, Unleashed. Now we have a new gameplay style, why would we make a connection to the old days?
Sega will almost Definitely treat it as if the "Dreamcast" era never happened, if they know what's good for the franchise. A re-release every now and then, but nothing more. We won't be getting any franchise continuations.
Unless they get bored, then we might end up with "Shadow the hedgehog 2"
yaaaaaaaaaaaaaaay.
(oddly enough, the idea of ShTH2 intrigues me, but that's for another time)