Jim Ryan confirmed this is NOT GT7 as expected (it wouldn't have made sense to create such a confusion if it was imo).
http://www.eurogamer.net/articles/2015-10-28-gran-turismo-sport-is-not-gran-turismo-7
Were not announcing Gran Turismo 7 at this stage, Ryan told Eurogamer plainly.
Fair to say [series director Kazunori Yamauchi] has been making these games for some considerable time now. I think its reasonable to assume that something else might come down the road. Is it a Prologue? No, I think itll be more that".
The old days, when the games were offline, the experience was defined by whats on the disc. You had a distinction between a Prologue and a full GT, it was very stark. When the game becomes more of an online connected experience, that distinction blurs. This will be much more than a Prologue type experience.
So basically it's a Prologue but since it's online,it can be trasformed into a service adding things and events and they're doing something new with the FIA they're not calling it a Prologue. At least they're confident they will deliver the game (not just the beta) next year.