Also, Apple has streamed their keynote online live at least once before. The stream was available via any iOS device, Mac, or PC that was running Safari.
I watched the live stream from my iPhone it muted while I was in band at school, I just had it sitting on my stand and the conductor never noticed xD
The time that they streamed, the recorded video was available online almost immediately after the keynote ended.
Also... there will likely be a spoiler free thread on the website somewhere if you're interested... it will block out all the news that happens during the keynote until Void's (or did some other forum member make it? I forget...) keynote checking script detects that the keynote video has been uploaded, at which point it'll give you a link straight to the video so you can watch it without knowing what will be revealed in advance. It makes it more fun and exciting to watch, at least in my opinion.