I'm not saying KZ2 and Heavy Rain will be bad games (personally I'm very excited about Heavy Rain after seeing the videos), but I'm saying that their sales are uncertain.
Tekken 5 did 1.64 million on 120M+ PS2s. MGS3 sold 4 million on PS2.
I think T6 will sell around 800k and MGS4 1,8M (LTD). And I do think that's so-so numbers.