I have a very very strong suspicion that the ffmpeg folks are not going to care one way or the other. If they were were very worried about patents I don't think they would of put so much effort into making h.264 codecs in the first place.
I think that google is treading very safe water here.
As far as H.264 goes for the web... The amount of bandwidth saved by using H.264 over Theora is more then enough to compensate for the cost of royalties for big players. For everybody else then there is Theora which should continue to have it's encoders improve the point to were at least it is somewhat of a rival for DivX. And like is mentioned you need to have H.264 for hardware compatibility and so on and so forth.
Dirac, it seems, is not going anywhere, unfortunately. Unless people are going to start concentrating on it after the Theora enccoder improvements are implemented.