MoP isn't getting the usual hype, and we all know why, but I don't think it will matter it will likely do as good as any other expansion. But I just don't think there's a demand for beta access as there was for Diablo 3.
Cataclysm was a let down. At least for me. It seemed like they put old contents, added a little color, and boom, Expansion set.
When they first announced MoP, I really though it was a joke (Like really, I waited for the trailer to end like : GOTCHA!!!). I really thought it was the end of World of Warcraft for me. 7 was a good number to leave.
But hey, believe it or not, months later, I'm really impressed by the word Blizzard is putting on this one. I am not hyped because I moved on, but I am definitely going to give it a try once it's released.
I have access to the beta, but I didn't even care for it. I did that for Wotlk and Cataclysm : Got burned out playing beta even before release.