One thing I know is, Blizzard expansions usually greatly improve the original. Frozen Throne was far better War III, Lord of Destruction was better than Diablo 2.
However, those games were aclaimed when launched and the expansion improved them. Or at least people used to say they were good. This was before the internet and I believe people enjoyed stuff more before Metacritic.
I'm more curious of what they will change, of what they will remove, what they will add. I'm not even saying the expansion will fix the problem but I'm interested on how they will try to fix it.
They may even make it right!