The Smithsonian will
not be doing a live webcast of this event; however, there is a chance that C-SPAN could opt to broadcast it live, but that decision will be very last minute. (As you may or may not know, C-SPAN stations broadcast live online in addition to cable and satellite, so, if whatever C-SPAN station it might be on isn't part of your cable package, you can still watch online).
Regardless of whether it's carried live, it will be available online afterward at some point.
Stay tuned.