I am guessing you will have plenty of time to buy it if you choose because i noticed Best Buy still carried the cata collector edition up to a year after its release and anyways The digital deluxe edition will be sold after release where you can upgrade your plain edition at any time for 20 dollars more
The one's for cata are still the same price if not lower so I don't think they will be selling out of mop ether. I've seen the same one at wallmart for like a year now cause they want $85+tax for it lol
I think the Guild Wars 2 is hurting the sales of WoW collector edtion. I remember the preivous 2 collector editions were sold out months before the release day. Now this Kung Fu panda collector edition is still available.