Given this is infinitely cheaper than using general purpose cores, why wouldn't you just build yourself an army of cortex m3/m4's and use them for video encoding now.
ARM doesn't really need to do anything here to make this happen. Since they give you all the chip related stuff necessary to build your own, just go and do it. If you want 64 m3's, go make it.
It's also not clear whether it's a SIMD solution. If that's the case, they are basically reinventing GPUs.
It is not SIMD. Each core is totally independent of the others. Basically the cores are structured in a grid, and all cores have 32KB in-core static RAM, but can also access the memory of all the other cores (at the cost of a few cycles delay), or main memory.
You could certainly use them as much like a SIMD if you wanted to, but then you'd likely get better performance out of a GPU.
We'll see when they deliver on their kickstarter project what type of performance people get out of it in reality...
Applied Micro also intends to introduce a 128 core SoC in 2014:
Also, keyframes are not known from the start in many encodings. A keyframe is inserted when the difference between a frame and the next one is big; this can only be detected when encoding, or with a multi-pass encoding.