Are you sure about that? TOR cost an insane amount to develop (300 milion USD I think?), and subscriptions dropped off really quickly. They mentioned considering going free to play not too long ago, and that's only like half a year after its release. And this is a franchise that is a lot more mainstream and has a lot more fans than Mass Effect does.
Even if BW recouped the expenses, I would expect them to think long and hard before starting development on another MMO.