Perhaps there should be a moratorium on the "but video is really secondary and I could do without it" talk, at least in threads with video-centric titles. This perspective has been voiced (with few points that elaborate on the base idea but many that demonstrate biased thinking) so often as to be implicit. The world knows some of you could care less about video, that you're all about stills. The argument now goes without saying.
The original poster is clearly interested in video, and anyone could see as much from the thread's title alone. Nonetheless, his original talking points have been only indirectly acknowledged. I don't understand why the anti-video perspectives hijack so many threads. It's not like pushing the "we don't care about video" agenda in the CR forums is going to dramatically sway Canon's thinking, especially since most of the arguments rely on anecdotal experience or emotional reasoning. Moreover, it's not like improvements in stills AND video are mutually exclusive. Allowing a "what do you think of this video feature" thread to evolve without anti-video interference will NOT change Canon's thinking. If there's some evidence that Canon's stills technology is lagging because the company has redirected too much R&D to video, then perhaps there's a valid gripe-- but I don't often see this sort of argument. I also doubt that it's the case.
Is the HDSLR video revolution a little played out? Given the surplus of shallow DOF fetish videos and time lapse movies on YouTube, sure. But this doesn't invalidate the entire enterprise so much as attest to an age-old truth: better tools won't necessarily make an unimaginative person more creative. But the technology is used in innovative and engaging ways by many, including some for whom traditional camcorders would be inadequate and non-DSLR large-sensor video cameras prohibitively expensive. Plus, some people actually prefer (notwithstanding "limitations" that require elaborate rigging) the DSLR form factor for video-- something the DSLR-inspired design of the C300 demonstrates. In short, video is here to stay. If someone has a more substantial criticism than "SLRs are supposed to be for STILLS, darn it," that's one thing. But a lot of the commentary fails to evolve beyond this (not altogether cogent) idea.
As for the OP's original point, I think Canon will have to reassess the clean HDMI output-- but if they weren't convinced the C300 required it, I'm skeptical that this move by Nikon will force Canon's hand. That said, the fact that the EOS division has to negotiate a bit with Canon's broadcast division seems to give Nikon some relative flexibility, at least for the present. That latitude could allow Nikon to aggressively pursue some things that Canon has been sheepish about. I'm still uncertain about Canon's likely response, though. In certain ways, the C300 is less impressive on paper (at least for the price) than the FS100, let alone the F3 or Scarlet. The reviews, however, have suggested that Cinema EOS is a pretty impressive new system, it's lowly 8-bit codec notwithstanding. If Canon is similarly confident that 1DX vs. D4 tests will bear out the merits of their product, then I doubt they'll change anything for now. The photographers at whom these cameras are targeted won't buy cameras based on specs alone, since virtually all of them will have glass investments to consider and enough experience to know that press releases don't translate into the best product.