We made an attempt at putting together a sort of roadmap  in the past and also some wide-ranging threads about what could be on it . and I think we should pick it up again. The description I really liked was "strategic and user impacting initiatives (ongoing and future) in an easy to consume format" . It seems that we had feedback asking for a Roadmap at the London summit .
I would like to first focus on meta-questions rather than what would be on it:
- What style / format should it have to be most useful for users?
- Where should it be presented?
I asked a couple people to try to find the roadmap on the web site, as a test, and they didn't really know which tab to click on first, so that's a starting problem. They didn't even find Works In Progress  after clicking Contribute. The level of detail of that list varies widely.
I'd also love to see hypothetical formats for it, to see how to balance pithiness with crucial details.