After a fairly testy exchange at BearHugCamp this morning among Steve Gillmor, Dustin Sallings (twitterspy and IdentiSpy bot creator), a few audience members and the guys at Twitter, Alex Payne actually gave a very clear statement about the lengths to which Twitter was willing to go to aide developers in building upon and extending Twitter.
If you need to poll the API more frequently that the API limits allow, email Alex and chances are very good that you can be accommodated. Ditto regarding something Alex referred to as a "research project" involving a data-mining feed -- presumably, this is like a customized (or perhaps random) fraction of the full public timeline firehose.
As for the full public timeline firehose via XMPP: "That would require a business discussion."
My Twitter bot works just fine for me, but Dustin is actually trying to provide a service to people other than himself, so he needs more cooperation from Twitter. Based on what Alex said, it seems that Dustin and others who are working on various bots to bring back the "track" feature via IM should be able to do so.
As for the "official" return of "track" and IM -- don't hold your breath.