I haven't seen an official announcement. That may be due to the fact that John is still working on all the new features.
"One question I have in particular: is it possible for some articles to be posted simultaneously to both forums, to allow both on- and off-topic discussions?"
No.
"The General Interest Forum hasn't reached "feature parity" yet with News/Activism. For example, the "Notify" pager won't trigger for pings from General Interest.'
I'm making an asumption, but as soon as the regular stuff is completed, John will have this worked out too.