next year: RX-200 with 100-360 zoom equivalent?

Have you ever seen a tele version of the Sony R1, the Canon G1X or some of the "premium compact cameras"?
I have not.

If you want a 2nd camera to add tele options to the RX100 why not buy a Panasonic FZ200.

It offers a real tele lens and picture quality should be quite fine at low ISO (and RAW).

You can also wait for a tele lens on the Nikon 1 system (and Nikon using that 20MP sensor) or you can buy a mFT camera with one of their tele lenses.

A pocket sized zoom lens going to real 150mm will most likely not happen.

Ok, they made such zoom lenses in the day of 35mm film cameras, often those lenses had something like F11 as their fastest aperture on the tele end.