You have two options: Get wow now and play through the old content before it all goes away in cataclysm or wait for cataclysm and play through it then.The Cheezy One said:I have never so much wanted to get into WoW. Should I get this first (as well as WoW), or just play through it one piece of Expansion pack at a time?
I would just get the original first and then get the burning crusade (1st expansion) when you hit level 58 and wrath of the lich king (2nd) when you hit 68 and finally cataclysm (3rd) when you hit 78 (or 80).
If you start now you'll have about two months to get to 58 before the old content is lost (plenty of time, depending on how much you play it will take 3-6 weeks on average (and of course some people do it in more and some in a lot less))