Proposal: Vi and vim
There was already such a proposal and it was declined. Don't follow this.
Reason was that VI and VIM are on topic on SO and a separate site would pull content.
Note that the discussion on the deletion of the previous proposal has been deleted.
As there was valuable content and discussion there, the only reason the Stack Exchange team could have decided to delete it is if they might be willing to reconsider the Vim site.
At least, that's what the optimistic side of me is thinking. :)
For reference, the overwhelming opposition to closing and deleting the Vim proposal is archived here.
I can't find the proposal page you're talking about? Do you have a link? EMacs seems to be in beta, so why not Vim?
There are already many other SE sites which overlap, such as SuperUser & unix.SE, or SuperUser & AskUbuntu; there are many other examples either already live, or actively being discussed.