This game is probably going to be great, but they fucked up bad not getting it out before diablo 3 (as well as PoE they screwed up as well).
Their sales will be a shell of what they could have been just because Diablo 3 will probably have so much content.
Would have been nice, if they released TL2 before D]l[, but I still think there is a hungry audience for this game. I think Diablo ]l[ will help fuel people to buy Torchlight II, they will get hot for Action RPG's again this Summer, and after playing D3, they will want something new again to tackle, or maybe D3 is not that great, and will be willing to try a different but similar game.
Plus the price of $20 for Torchlight II is too hard a deal to pass up. I think the $60 price for Diablo ]l[ is insanely high. I am much looking forward to T2 over D3.