Look. Video compression is a field that is patented to hell and back. As long as Theora aims to remain patent unencumbered, it has to avoid so many things that could make it better that its utterly ridiculous. x264 developers have to care about absolutely none of these.
Also, as it is, x264 development is a lot more active than libtheora development is. From the beginning of 2009, Theora has received about 42 updates. In the same time, x264 has had 440 revisions.
The only way libtheora could ever beat x264 pretty much requires that software patents stop existing, and at that point we wouldn't even need it anymore.
Thus, libtheora will never beat x264 in quality in speed.