The Nikon 1 J5 specifications suggest it will have both a 20.8MP sensor and 4K video.
Nikon has previously allowed for a very short 4K burst mode on the V1:
Quicklapse is a way of extending the burst shooting rates that digital cameras have (like 4 or 5 shots per second) by using software to generate the frames in between. There are of course limitations to this technique and the type of subject matter that it works for.
Sanchez & Olaso, who specialize in architecture motion photography, have released the following example of their 8K video with the aforementioned quicklapse technique:
See the Sanchez & Olaso website and their blog post titled Behind the scenes – Capturing 8K Video at Son Brull hotel for more information.
Nikon Rumors reports on the upcoming Nikon 1 J5 and state that it is rumored to have 4K video capabilities. No Nikon camera has 4K video to date. While Nikon has staid true to its photography roots it’s never been clear why they have not attempted to provide high quality video features as they have no video camera market to protect.
The Nikon D7200 is expected to be announced soon as well, however there are no rumours of indications of anything other than 1080p video for this DSLR camera.