I don't see this coming too fast - if ever: there is no shutter, and for now there is no electronic shutter (if even possible with this sensor). So only lenses with shutter inside are an option. Rolleiflex 6000? Well, not really - they are monstersa manual adapter should be no problem at all. Probably in a few months for 20 USD on ebay from HongKong. The third party industry was always fast with adapters for mirrorless systems.
I'm more surprised that they developed (as I understand) around this quite small sensor (in MF terms). It's only a fraction bigger than a 24x36mm, especially if you prefer 2x3-format (those who prefer 3x4 of course have bigger advantage). Having the 42x56mm sensor as an option would have been nice for the system. But of course whould have made bigger lenses. But with this relatively small sensor they have to compete with a (for sure) coming Sony A9 (with maybe more pixels, better AF, more lenses - and all for maybe half price). But we will see - Leica S also has a not sooo big sensor and seems to sell...
Having said this - I really like the camera. It looks great, ergonomics seem fine.