Well, if the rumors (and all the hype currently being thrown around in the press) pan out, MSN and Yahoo will, all of a sudden, have a lot more on their minds (sorry AOL, but AIM would rate zilch on this side of the Atlantic if it weren't for iChat and .Mac - as it is, it's simply irrelevant).
As far as I'm concerned, IM is not really an issue. Except, of course, as a very nice way to leverage Google's existing Gmail user database (and keep in mind that those users basically recruited themselves, and besides the video attachment junkies that have been sneaking in of late, they're a pretty loyal bunch).
IM is, in many aspects, a cheap service to deploy (even more so at their scale), and if they're going for Jabber... Well, let's just say it will be the second credible implementation I've seen (nod to Melo and the Sapo gang). And it would be nice if they cut the usual crap and let standard Jabber clients (like Adium and modern iChat) connect to their service (the only thing that would really bug me is if they archived conversations for searching, but hey, that's me).