Hm, I'll be the asshole and point out something that to me is kind of obvious: Bootstrap isn't mainstream enough to warrant it's own foundation/organization.
Just looking at the caliber of other projects that have gone this way (at the top of my head: Apache, Drupal, Django, Zope...) and looking at Boostrap I don't think it's even close to the userbase/clout needed to pull this off. Even the maintainers of those other projects, successful as they are, tend to have a day job.
I don't know, maybe I'm reading too much into this, but I think it might be a little to early to make this move. Just my 2c.