I'm actually curious... explain why you think that. I know that Bioware makes good RPGs, and I am very interested in playing the Old Republic. However I want to know how you think it will compel WoW players to keep playing it beyond the first month or two of its release.
Sure, I'll elaborate.
Bioware is like Blizzard, in one sense - a very well respected company. Look at their back-log of games and for the most part, you find a lot of greatness - Baldur's Gate series, Dragon Age: Origins, Mass Effect series, KOTOR, NWN: Hordes.
Also, we're talking about Bioware is again working with one of the biggest franchises of all time here that Bioware is working with - Star Wars. Unlike most of the MMO's out there, Bioware's going to have for SWTOR full-supported voice-acting for this one. The decision-making stuff found in most of their Single Player RPG's are also going to be here. Given that Bioware seems to also have a knack for releasing tons of DLC at a very face pace for their most recent games - see DAO and Mass Effect 2 - I think we'll see a lot of that incorporated into SWTOR as part of that $15 per month fee SWTOR will likely have - that'll keep players playing. Also, EACH class has their own specific storyline, as well - so, likely, if you want the whole story, you're probably going to play out every class.
I smell the evolution of the MMO right before our eyes right here...