"to answer your question, no, it won't sell as well as previous installments that's for sure".
and you have proof of this?? I mean for sure???? you got a time time machine O_O,
sounds more like wishful thinking.
now fact: both GT1 and GT3 being the first GT titles on a playstation console just like GT5 both went on to sell the most in their respective generations over the squeals on install bases LESS than what the ps3 currently has,
so please tell me how the hell GT5 will with out a doubt, despite having more content than any racer released this gen, sure shot at AAA on a larger install base than the ps1 and 2 at the release of the first GT titles on those console will sell anything less than previous installments??