Who else is going to be there?
I think the current meta (I call it 2.0) for short is well suited for a number of issues pertaining to day-to-day operations and to the SE interface, and 2.0 is ill-suited for the long term discussions that need to take place to keep MathOverflow the idea going. However, if there is only a small group interested in using Discourse, then I recommend using the old Vanilla forum, with someone updating 2.0 periodically with a summary of goings on.