Sony isn't EA, so I'm not exactly "worried."
Then again, while I play D2, it's not a game I cherish... nor do I think there's anything really to ruin by this acquisition. We all know the general grind for D2. And, the story is like background noise if you haven't played since D1. D2 is straight loot shooter. Any RPG elements that made it unique and interesting was left in the D1 era.
I would be more "concerned" if Microsoft bought D2... Sony actually lets its developers go do their own things (in general) and not dictate nonsense (RPG developer - yeah, you don't do that anymore. You do loot shooter).