That would honestly suck. I've been playing since the original beta, and some of my older characters have... embarrassing amounts of /played time on them. If TOR is awesome, I'll just forget about them anyways. But, if for some reason TOR fails and ends up F2P, I'd like to still have all that stuff I've gained over the last 7 years on my WoW toons.
Also, even if I'm really into TOR when it comes out, I'll probably try MoP for the hell of it. Unlike a lot of people, kung fu pandas sound freakin sweet to me -- And actually the drunken tiger fighting style of the tank spec is what I've been wishing for since day 1 of WoW. lol