Interesting, from Chris Yost via a LiveBlog event on Marvel.com:
"Avengers is neither sequel nor spiritual successor to 'Wolverine and the X-Men' -- it's the Avengers. But they were more or less intended to be in the same universe. Regardless of which eye Fury's patch was on. "
Also, since some mused earlier: Scarlet Witch and Quicksilver ARE available for use, and there will be non-Avenger guest stars.
EDIT: Here's the preview for next week: http://www.youtube.com/watch?v=UBoFZjD29cA