My guess is that it will be optional. Something will probably happen in OWB that makes this happen (whether it is a simple pop-up message that allows for the respec like when we are leaving Goodsprings, or it may happen in the DLC itself as part of the story or a feature that is within the area. Anything can happen).
As far as what it is I believe it will only affect the character's traits, but perhaps other things (such as our appearance) could also be possible. I do not believe our alignment to factions will be altered, though Ulysses may prove otherwise...