MPEG4 should kill DivX.
It has AAC audio encoding, providing for higher quality, lower data rate audio.
Its video codecs will be much more scalable, providing video from cell phone quality up to DVD, at data rates suitable for the web.
DivX is a non-standard codec, and causes problems for IT people like me who have to try to make video that people have encoded using DivX work for some web-based instruction and testing. People complain enough about Flash and QT plug-ins. Codecs are even worse...
I agree with TechLarry, DivX's rep for being used for pirating movies and distributing porn will prevent it from being accepted as a commercial solution.