OK the new RX100MKII seems to be better in low light (faster focus), has a tilting screen and a hotshoe for flash.
But sadly, the announced increase in sensitivity is not real, now it start @ISO160, ISO80 not more available, and ISO100, 125 are expanded modes !
The sensitivity increase is real, but it is through an improvement in the fraction of light detected (sensitivity to light), not a reduction in read noise. So an increase in the base ISO sensitivity is exactly what one would expect --- and one can also expect an increase in any noise-based measure of maximum usable ISO sensitivity setting, and improved signal-to-noise at any given exposure level (ISO setting).
What it does not give is an increase in _dynamic range_, which seems to be what you are hoping for. That would instead require reduced read noise (or increased well capacity).
One milestone for this camera is using back-side illumination (BSI) on a larger sensor than ever before: 13.2x8.8mm (so-called 1"). For a moment I wondered if this is a sign that BSI will soon move to the sensors of some system cameras. But with 20MP, this sensor still has quite small photo-sites, with a spacing of 2.4 microns, so maybe BSI will only make sense for system camera sensors if and when their photo-sites get that small, which would be 38MP for Four Thirds, 63MP for Sony's version of APS-C size, and so on.