In the mean time, the Microsoft Internet Explorer team announced that in IE9 they are going to support HTML5 and that H.264 will be the only supported video encoding standard.
There is a truckload of hardware that supports H.264 decoding acceleration.
So the movement is from a plethora of video encoding standards into one broadly accepted H.264 standard.
When you look at the combination of support in HTML5/H.264 for all the major browsers, only FireFox has not announced support. This is probably because H.264 is not a free (as in beer) standard: commercial use requires payment. But – if I read the H.264 article right – content that is free for end users requires no royalties to be paid.
This combined hardware and software support means that there is a pretty strong backing for H.264!
Reference: IEBlog : HTML5 Video.