Another rumor
I know this isn't as big as the SA3 rumor going on, but SEGA is planning a modified version of SA2.
A remake, with possibly the same story, with 2012 CGA than the 2001 CGA.
http://gamingbolt.com/sonic-adventure-2-hd-announced-for-psn-xbla
Result: CONFIRMED!
http://www.escapistmagazine.com/news/view/118542-Sega-Confirms-Sonic-Adventure-2-HD