http://www.gamesas.com/index.php?/topic/1102578-brink-beta/ so let's continue this discussion in there. Of particular interest is this post from one of the Community Managers:
Paul Wedgwood answered this recently.
“We’re still talking about what the right thing to do is there. In terms of project status, we’re pre-beta, so we’re doing a lot of balancing, working out what works, what doesn’t, cutting things, that kind of thing.
“Probably when we get to around beta, we’ll make that decision, then Bethesda will make any announcements.”
http://www.vg247.com/2010/05/07/splash-damage-still-talking-about-possible-brink-co-op-demo/