Definitely not live - only about an hour or two after the show. There are, however, several online publications with text transcripts, some with pictures, others even try a kind of live radio broadcast, I've heard.
I don't recall where I read it from, but it has already been announced that the keynote will be available from Apple.com [a few hours] after it happens.
Too bad hardly any ISPs support multicast. If they did everyone would be able to watch it live and it wouldn't use hardly as much bandwidth as individual streams.