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.
EDIT Having seen the Discourse page, I can see where it could lead to the kind of brainstorming and collaboration needed for the future of MathOverflow. Again, I think it is important to know how many will participate. The forum publishing.mathforge.org of Andrew Stacey was and still is a good idea, but it seems to have very little traffic nowadays. MathOverflow cannot enjoy its current success without continual efforts to moderate, promote, evolve, and discuss. I know I don't want attempt such discussions on this meta.