This is a good point to be made. Besides the times a-changing, Adventure-era Sonic was designed to be a teenager. I'm laughing hysterically as I type this sentence, but Sonic was canonically 15 or 16 years old during this time. Of course he was an awkwardly lanky, douchey teenager (who made some questionable decisions and friends, coughcoughTHEGAMEScough); he was kinda going though puberty. :V
But see, now they don't really say much about his age anymore, he's mellowed out, his voice keeps getting deeper, but still kinda cheesy. They're making him more "timeless" again. Beyond the implication, I think at one point Sega outright said that he was celebrating his 20th birthday in Generations.
In conclusion, Sonic the Hedgehog is aging.
Sega also said that game isn't cannon. And said classic sonic isn't( frequently) coming back. Then hinted at trying to include more characters in the games.
I don't think they are trying to make him timeless, because timelessness isn't exactly a good thing, that status quo is a hell of a something. I think they just want to do what they were doing better than they were doing it.
Sonic being a teenager didn't magically make sonic 06 bad, sonic team making a shit game made it bad.