The discussion forum and EE templating and memberships are not interchangeable. There is no current Ellis roadmap in that direction. More discussion forum developer addons such as forum subscribe and RL forum themes will really help. Many of the top EE developers still recommend comments be used instead of the forum.
A GREAT example of a customized Discussion Forum 2.1.2 is http://www.solspace.com/forums.
This EE forum thread shares posts on discussion forum that will give you insight as you plan:
Who wants a better EE forum?
Tim M - EE Dev Posted: 13 March 2011 03:11 PM
http://ellislab.com/forums/viewthread/183513/
Good luck with your projects. EE is the best. Hope this helps
Chris