If it is indeed a HD port of an older game, then it's not far fetched to think it's not the only one. Sega seem to do these in batches.
First batch
Sonic Adventure
Space Channel 5 part 2
Sega Bass Fishing
Crazy Taxi
Second batch
Nights into Dreams (it's a PS2 port, right?)
Jet Set Radio HD
Sonic Adventure 2
I think it's reasonable to expect some other last-gen games will be joining it, if that's the case.
So what've we got left over from last gen days? Shenmue I & II? Phantasy Star Online Ep 1 & 2? Headhunter? Panzer Dragoon Orta? Jet Set Radio Future? Anything else I'm missing?
The numbers are slowly narrowing down, and I'd really love to play PSO, JSRF and the Shenmue series in HD.