In my country the a6300 is 1400euros body only, and 1600 kit, similar money with a slightly used A7s.
m4/3 people have their Olympuses for stills and Panasonics for 4K video.
Fuji said that they are about to give 4K in a firmware update, so they must be about to do it.
I do not see a lot of NX users to HAVE TO switch (NX500 is doing crop 4K for 499euros kit, NX1 is probably a better PRO camera than a6300, but I am not going to debate now), except the ones that abandoning ship (but it doesn't mean they go Sony, a lot have gone m4/3 already, for small and light lenses, or Fuji for APS-C).
Nikon they will have their own 4K camera soon, and it will be interesting to see if they have built to their excellent HD files as well.
Canon users they do not know about 4K, and the ones they do buy C300mkII or 1D ( I am being sarcastic, but the Canon policy actually works for them!)..
Pentax they have their own new Full Frame camera to play with, so I am not sure how many people will buy to this camera, simpler users with a6000 and a5000 cameras will be reluctant to upgrade, as the price is not that good (yet) and maybe the lowering of a6000 will be a more attractive option to them. The not many APS-C native lens options is something to consider too.
I can see every A7 owner to get one though, as a B-cam, or every day "compact", but the camera is not that groundbreaking, maybe the a7000 will be (touchscreen in the year 2020 for Sony, while car and white appliances have already!), but we haven't seen the a6300 yet..