Triple RX100 IV test by Dpreview, Philip Bloom and Ken Rockwell.

Dpreview posted their first impression review:

The RX100 IV fits pretty well in your hands, though those with large hands might find controls to be on the small side. The camera can be operated with one hand, though you’ll need your other hand for rotating the control ring around the lens.

Philip Bloom tested both new RX cameras and writes:

The 250fps (240 in NTSC) is excellent when in “quality mode” although just 2 second buffer and a 20 second write to card time. The 500fps (480 in NTSC) is passable on certain things, avoid hard lines if you can as it will moire and alias like crazy! 1000 fps (960 in NTSC) is ugly as hell but I still managed to get away with it in my test film. In the real world I can’t see me using past 250 fps very often. The modes where you can record twice as long are much poorer quality so I avoid them.

Ken Rockwell also tested the new RX100m4 and writes:

The RX100 Mk IV is a fantastic point-and-shoot camera that quickly and easily makes great photos in any light, and its larger-than-most point-and-shoots sensor giving sharper, cleaner images than cell phones or most other pocket cameras.

Call the Cleaner! Sony RX100 IV 250fps, 500fps & 1000fps from Philip Bloom on Vimeo.

A7rII and RX camera preorder list:
In USA:
A7rII at Amazon, BHphoto, Adorama, SonyStore US, FocusCamera, Uniquephoto.
RX10m2 at Amazon, BHphoto, Adorama, FocusCamera, Uniquephoto.
RX100m4 at Amazon, BHphoto, Adorama, FocusCamera, Uniquephoto.
In Europe at:
A7rII at Sony DE, UK, FR, IT, ES, NL, BE, CH, AT, SE, FI, NO, PT. Wex UK.
RX100m4 at DE, UK, FR, IT, ES, NL, BE, CH, AT, SE, FI, NO, PT. Wex UK.
RX10m2 at DE, UK, FR, IT, ES, NL, BE, CH, AT, SE, FI, NO, PT. Wex UK.
In Asia at:
A7rII at Digitalrev, CameraPro.
RX10m2 at Digitalrev, CameraPro.
RX100m4 at Digitalrev, CameraPro.