Its hard to say.
Depends on Forza 5. Remember if Forza 5 is at E3 playable and is really moving forward with next gen hardware, I feel it may affect what reviewers think come reviewing GT6. They may compare it unfairly to a next gen forza. Which I think would be unfair. They should just compare it to current gen games.
I say it could be anywhere between 80 - 94 due to this possible variable.