Hi,
There is a Request for proposals / Statement of work for vendors interested in being involved in the development of this project:
http://www.mediawiki.org/wiki/Requests_for_comment/Wikitech_contributors
We are still discussing the proposal in the community, but in any case we need a better idea of the resources and budget needed. If you have any questions please contact me.
By the way, the proposal might be interesting for other wikis with a community of contributors. Your feedback in the wiki page e.g. based on your own projects or your needs is welcome as well.