I have been playing WoW now for 4 years now so I missed the hay day of Vanilla, I started at the release of The Burning Crusade and spent way to many days not studying playing. I do have to admit that since the release of Wrath of the Lich King I did start playing a whole lot less down to playing only 2-3 nights a week most weeks. Through Cataclysm I have wanted to play more but have not had the time due to real life changes for the best.
But I am really excited for Mists of Pandaria because it is new and unknown, where Cataclysm kinda let us down with only 2 truly new zones, Tol Barad, and 2 starter areas that were new, I was really looking forward to going to Undermine. Uldum was a let with 6 years of build up of wondering what was behind those doors. Hyjal a fun zone but it felt very familiar and Twilight Highlands was the same. With Wrath it was new in a WoW sense but in Warcraft it was not. So with Mists we should get that sense of excitement of going somewhere new like we did in Vanilla and TBC.
And this whole notion of Kung-Fu Panda will ruin the game, is bogus the Pandaren have been around since WarCraft3 and have been a race that me along with many long time Warcraft fans (not necessarily wow fans) have been eager to play. Pre-TBC they were even thought to be the Alliance playable race for the expansion.
I did signup for the WoW annual pass so I will be in the MoP beta however I don't play on PTRs much because I like being surprised with content that I will be playing through for 4-8 months, so I am still torn about actually participating in the beta.