How Many More Expansion, Blizz?? O_o

I'm not exactly sure where I heard this, but I was told by several people that Blizzard intends to make four expansions in total (BC being the first one) for the game before WoW officially ends. Well that's all fine and good, if it's not TRULY the end. Everquest (even though I don't like the game) created a sequel with updated graphics, and Diablo 3 is coming out with a full overhaul.

It's probably FAR too early for me to be thinking about this, but as I level up and gear up and raid epic dungeons, I keep getting this little nagging feeling in my head that 'The end is near" and "it will be over soon" and "you're wasting your time, it's all DOOOOMED..."

... As I said, probably too early to think about.

Anyway, if any blizz employees are reading this... is there any word on just how much longer WoW will last? And when it does eventually end, will there be a WoW 2 afterwards? I heard there would be another MMO project by blizz not related to any currently existing franchise, and I've grown a bit attached to Azeroth. :)