alilown
(2) is what we have been mostly doing for the last couple of years, but our Java6+GWT+Ant+Subversion (only recently switched to git) stack was failing to attract new developers. There were several calls to rewrite the entire thing in (say) javascript.
Chat integration is arguably simpler - and Wave already understands XMPP (for federation), so it would be possibly to map Jabber -> Wave (say). How you would want to map from Wave -> Jabber is more complicated (as any blip at any point in the tree, can be edited at any time, by anybody)...
There is no roadmap, as we do not (yet) have a large enough consistent amount of developer power to benefit from one. Most of the patches we receive are fixes/improvements that benefit the submitter (e.g. full text search, monogodb backend, etc.)
Sorry about the downloads page, you saw the page as prepared for an actual release - I have rolled it back to showing the last release candidate presented on the mailing list.
Feel free to ask me any other questions...