I'm in the same situation as OP. I have a few more quesetions (please try to avoid spoilers):
Do we already know if the addon will take place after the main story, or will it be parallel/right from the beginning?
I guess it would make a difference if the new companions would be available quite early or only in new addon areas.
If I start playing and later install 2.0/WM, will I be able to continue from my save game, or will I have to start over?
It may very well be that nobody can answer those questions yet, but no harm in asking, right?