Microsoft will livestream its official Windows Phone 8 launch event on October 29th 2012. From the Microsoft blog:
As many of you know, we are landing in San Francisco on Monday October 29th to showcase some new things from Windows Phone. For those that can’t join us in person, no need to worry! You can tune into a live webcast here, all from the comfort of your couch, cubicle or coffee table. We hope you can join us, see you on the 29th!
The event starts at 1000 PST (1300 EST).