They cannot be revived by the DO.

However, there is no indication they won't be respun, and every indication they will be.

Also, at one time, a Q & A session with RJ implied that the DO had a limited time to use his power to reclaim someone's soul.

And since balefire back-killed people, he had even less time, and thus could miss his chance because there was even less time. Plus he needed appropriate bodies and didn't just keep them on hand.

That left a theoritical loophole--someone like Moiraine, who had very weak balefire, could balefire someone that the DO could still bring back.

But, since Be'lal never came back, it seems that maybe that isn't the case.