Heavenly Sword 2 is very much a game I would love to see. However, I bought it late a decent price and feel it was justified. If I'd have paid £40 for the game when it came out, I'd feel very ripped off.
Therein lies a missed opportunity for Sony and Ninja Theory, in my opinion. The work was already done with Heavenly Sword - engine made; characters designed; combat defined; universe set out. I'd imagine there would've been a significantly smaller amount of work involved in making a sequel, which could potentially right many of the wrongs of the original (it was too damn hig... err, short). They should have at least tried to work together to see if they could get it perfect second time around.
Combining what Pezus and HappyD said, I think there is an inherent problem here. There is a lot of free publicity and sales loyalty from making a game exclusive, and it's something that both Ninja Theory and now my beloved Insomniac have fallen foul of. Both of the teams make "good but not great" games (even though I love Insomniac and that's hard for me to say), which is more the problem here. A game of that calibre, I feel, will cost less and sell more if it's exclusive. So unless either of them step up to become an AAA studio, they'll have a hard time in the wilderness of multi-platform development.
Who knows what the future holds. Maybe we'll see them both return to Sony, or maybe they'll both really crank it up for their next titles. Ratchet on PS4 is a shoe-in regardless of how badly Fuse does (unless it kills the whole company); but I would be very excited to hear if Sony could get NT back so we could see Nariko & Kai again.