MattyC, Starcraft (2+ years) and Diablo 2's (3-4 years) development times don't compare to their sequels. You don't think Diablo3's 10+ years was at all excessive? In that timeframe Bethesda released THREE Elder Scrolls games (not to mention Fallout and the expansions).
I like the quality from Blizzard games too, but enough's enough man. I could see 10 years being needed for a very ambitious, genre-busting game, but pretty soon "playing it safe" is going to bite them in the ass if they continue along at the same pace they're going now. None of my friends bought Diablo 3 or Starcraft 2. We played the crap out of the old games. Inevitably though, fresher games came along that made us lose interest. That's what I see happening unless Blizzard's Titan becomes that new killer IP. I have my doubts. They've been riding that huge wave from the 90's for too long.