Sony has announced the NEX-FS700, the latest in its line of professional video cameras. It builds on the previous FS100 model, with a large Super 35mm sensor and the same E-mount used by the NEX still cameras, but the FS700 will be capable of 4K video shooting... eventually. There's a slight catch with this feature as it won't be quite ready out of the box, so you'll be shooting 1080p at first, but via a future upgrade you'll be able to record 4K video over 3G-SDI to an external recorder.
This addition would take the FS700 beyond the resolution of Canon's C300 into RED territory, and likely at a significantly lower price — though we haven't actually heard word from Sony on that crucial point yet. Other features include built-in neutral density filters and super slow motion recording up to 10x at full HD resolution (40x at an unspecified lower resolution). We don't have official confirmation of a release date yet, but SonyAlphaRumors says it'll be available in June.