You could harness the Pi' GPU by creating a plugin for mediastreamer2, but this is hard work.
Also, you could use an armv7 toolchain and recompile the python wrapper with NEON enabled for VP8. I've done it, it is not too bad, but you won't get stellar performances. It seems that the USB interface for the webcam sucks too much I/O for the CPU to be a bottleneck.
I'll try to review my patches for the build of the python module and maybe publish them. You have to do it under Archlinux for Pi2, on the Pi itself, though.