> However, along these lines the removal of Jabber support
> from Gmail is a little bit scary (first they removed
> federation support, then they killed it altogether)
Federation support was temporarily disabled, then re-enabled once they got spam filtering in place. Currently, XMPP works perfectly with a Gmail account.
> My understanding is that upgrading to Hangouts still
> disables the old XMPP support.
Sort of; the web interface will connect to either Hangouts or XMPP, but not both at once. XMPP continues to work fine for non-web clients, such as Pidgin.