Seems to me they've been winding down for some time, what with other projects - Kim with her art & fashion, Lee's audio-visual things with Leah, Thurston's endless side projects & increased solo song-based output & tours, Steve jus' kickin' out the jams with whoever the hell he fancies because he's Steve fucking Shelley and everyone wants him to be in their band. The gaps between releases has been steadily increasing and the group chemistry seems stilted: I really didn't rate The Eternal and from the gig reviews I've read it seems as though on stage they haven't been too hot either. I mean, before you even factor in the whole K & T split, the music seems to have been laboured for a a while now.
As shit as it seems, perhaps it's time for them to call it a day. True, there won't be any more Sonic Youth product (other than God knows how many hours worth of archival material for repackaging), but they will still play music together: Steve has appeared on Thurston's solo stuff and is set to play on Lee's album, Thurston and Lee have recorded non-SY bits together, ie: with Connors. I suppose the one who may be more out of sight is Kim. Her solo/other musical endevours have been with other women generally and haven't tended to included any of the other SY members.
I suppose that what I'm trying to say in a roundabout way is that I'm sort of coming to terms with the more-than-likely-death of my favourite band.