Happy, I agree (obviously, considering KZ2) that a developer can improve upon a mediocre game in a sequel. However, I don't think it's common to go from 63% to 90%. GG went from 70% to 77% with Killzone (granted, different hardware) before producing Killzone 2.
Another example is Resistance, which was also a launch title so it launched the same weekend as Red Steel. It also had 2 years of development and only went from 86% to 87%. Red Steel obviously has a lot more room for improvement, though.
I'm not saying it's a sure bet to suck, I'm just saying that it's unlikely to be a AAA game.