The Z Cam E1 which delivered excellent quality 4k footage from a tiny package and was able to do 720p 240fps frame rates “at less than ideal quality”, however, a new Rumor from 4/3 Rumors here shows a Twitter message that hints at a new Z E2 m4/3 camera that is able to do 120fps at full 4k resolution. If this turns out to be true it could yield further performance improvements in 1080p and 720p along with higher quality that could be usable.
As far as linear specs go a 120p 4k pipeline could in theory yield 480fps 1080p and 960/1000fps 720p without going out of spec. As we have come to know over the years, however, it is usually wrong to extrapolate these specs to the maximum possible metric as the sensor or memory could be bottlenecks that limit the performance. So this rumor could have some legs to it and NAB 2018 could be the show that makes 4k 120p a regular feature for cameras.