Previewed at WWDC, launching in the fall.
Phil Schiller is giving the Keynote address which will be streamed live from Apple starting at 10:30am Pacific Time.
The most concrete information available on Quicktime Live and the potential for Quicktime 6.0 comes from this CreativeMac interview with Frank Casanova from December 17, 2001.
In it, Casanova describes MPEG-4 as a strong direction for Apple... however the recently released licensing plan is not being well received - due to a 2 cent/hour streaming fee.
MacWorld UK posted a possibility of a surprise at QuicktimeLive. This is actually hinted at by Casanova himself in the interview back in December: If you look at the program grid on QuickTimeLive.com, you'll see that we left a few of them open and untitled because, you know, anytime we get together we like to leave space for some really cool surprises, and QuickTime Live should be no exception.
More recently, CNet writes that One of the key announcements will be that QuickTime 5.1 will support MPEG-4
Note: MPEG-4 is not the same as Divx - the popular video compression codec on the net... however, many users are hoping that Quicktime Live will bring a long awaited update to Quicktime to allow it to properly read AVI's created with this codec. (see MacDivx for links)
As always anything (or nothing) can happen.