latest news about Eclipse 4.0-Collection of common programming errors
It’s planned to be a release the summer of 2010, but there will be an Eclipse 3.6 release and perhaps even a 3.7 etc. so it’s to separate tracks.
On EclipseCon 2009 there was a lot of talk about how the user interface is going to modelled (using EMF), but there will be compatibility layer so you will be able to run your old plugins in e4 without large rewrites, if any.
They also talked about the Eclipse Runtime, which is way to use Eclipse functionality in other ways than just in the IDE, e.g in middle-ware.