My friend recently got a new Apple macbook pro which came with the ATI 4650 Mobility and runs Modern Warfare and WoW with no problems at max settings.
I believe they are now coming with the Nvidia 330M graphics board, which should perform on par with the ATI one. Not going to give the same performance as a high spec desktop graphics card but more than enough to run WoW.
My current Acer laptop with an ATI 5650 Mobility runs it fine too (has about the same performance as my old desktops 8800 GTX).
For a while I ran WoW on my work laptop which has an ancient ATI X1250. Had to run with minimum settings but it ran.
To summarize, yes. The new macbook pro will run WoW with decent, if not maxed settings.
But if you don't really need a laptop then a desktop would offer better performance and future proofing for games. If you want a laptop but don't specifically need an apple for media work or some other purposes, consider getting a PC laptop instead. You can save a lot of money and get something with a more powerful graphics board.
When looking to buy laptops I find that Notebookcheck is quite useful.
http://www.notebookcheck.net/Computer-Games-on-Laptop-Graphic-Cards.13849.0.html
The chart in the link above lists all Mobile graphics and has results from tests of popular games. The 330M doesn't have many results listed and has a red mark at WoW at high settings but I think that must be because it hasn't really been tested yet. The 4650 which has similar performance gets something around 30 fps reported for WoW on high settings.