Wowza should easily be able to support VP8 once it has been added to Flash. As far as beyond Flash there is not any information from Google as to how streaming will work with HTML5. At this point it seems to be progressive download only.
And we sent a note to another developer doing work in this area with reference to this thread. Not sure where that will lead, but you may see a response here.
In our company we need to make the video encoder by FME as it does not find any solution to make the application in Flex and I think it will be possible in VP8. Have you had experience in doing the same encoder that is not in H.264 inside a Flex application or a tip? For using the spark to make encoder generates a very inferior quality.
I contact On2 for try VP6 in application but they were purchased by Google and do not know what will be the company.
And we sent a note to another developer doing work in this area with reference to this thread. Not sure where that will lead, but you may see a response here.