* angle of incident light (short flange distanze, lage sensor) - yes it is a problem. Yes, it can be solved, as Leica has demonstrated. Can it be solved for 10mm less flange distance, at far lower cost (than Leica) and still giving excellent image quality - I believe(!) yes, and I believe (!) it will be proven soon enough
Ultimately Leica solved the problem by redesigning lenses, this generally ment making them larger, I'd guess either having a less recessed rear element or a more telecentric design. Bare in mind of course that your not just talking expensive lenses with Leica(the cheaper Zeiss M lenses are generally larger) but also lenses that do not have to deal with AF and in camera aperture control. Just look at the difference between the Nikon 50mm 1.2 and the Canon 50mm 1.2 to see the difference just AF can make.
* Once Mirrorless cameras will finally be "really right", i.e. "solid state" with no moving parts whatsoever inside [=no mechanical, but global electronic shutter] will have a LOT of advantages over (D)SLRs beyond bulk and weight. Here are the ones I am interested in:
- 100% vibration-free operation = benefits to image quality, especially "when it counts" = in challenging capture situations
- 100% silent operation possible = ability to get any images or the images you really want in many capture situations e.g. concerts, churches, theaters, candids
- flash X-sync down to 1/8000s ... or whatever shortest exposure time will be = images possible, that are currently totally unthinkable
- higher image quality - no misalignment of optical axis and sensor/focus plane possible - provided lens mount is solid and precise
- lmore bang for the buck - significantly fewer parts, no moving parts = significantly lower cost to makers, due to easier assembly, precision-alignment, quality control = lower prices for cameras possible (!)
- higher reliability = no more mechanical defects possible, only electronic issues = significantly less failure in use, significantly shorter repair-turnarounds ... just swap out a circuit board, finished. No re-alignment of components required
- much faster cameras possible ... fps as high as we want them possible - only limited by procssing power and bandwidth - and those follow Moore's law, so we'll have plenty, very soon :-)
- better information at time of image capture - thanks to EVFs - which will continue to fast-evolve from "just acceptable in early 2014" to "absolutely mind-boggling" in the near future
And I am sure, we are still missing a few. :-)
You seem to be doing exactly what I said in my post, listing many possible advantages of mirrorless in the future and then putting that towards the idea that everyone wants a very small body.
* Relative lens size
does NOT scale 1:1 linear with sensor format! Not on SLRs. Not on MILCs.
Yes, 1" < mFT < APS-C < FF lenses. But with "really right" designs, the difference is rather small (ceteris paribus).
And beyond approx. 135mm physical focal length there is NO difference, since only the size of the entry pupil dictates size of the lens at the the end of the day. As evidenced by existing tele-lenses (mFT, FT, APS-C) and by the fact, that longer tele-lenses are not made for smaller than 135 ("FF") image circle.
My guess is that lens size saving will be harder to achieve in FF not only because light angles become more of a factor but because more effort has already been put into downsizing FF designs. You look at a lot of the recent L updates and shaving size/weight has been part of it because your talking about lenses large enough to unbalance even FF bodies. ASPC and 43 DSLR's didn't ever really have this pressure, the higher end models are generally not far off FF bodies in size so balance was likely far less of an issue with their design.
Looking specifically at m43 and 43 I view the switch from DSLR to mirror less as actually less important than the switch in emphasis of lens design. Oly's 43 DSLR's really weren't designed at all to be size savers and instead looked to pack more performance into lenses a similar size to larger formats in order to equal them.
That's why I expect some APS-C mirrorless systems to be around for a few more years, until everything gives way to FF. Anybody "really into" photography - whether professionally or as an enthusist/amateur - will get FF MILCs [sized very compact or as large and heavy as a current pro-DSLR for those who prefer "large and heavy"], everybody else only interested in "snapping a few" will use their mobile devices ... which will get better and better IQ in extremely small form factors [think Google glass :-)]. The middle-ground will disappear. But again, thats only my expectation, no fact (yet). :-)
Not sure I see that happening anytime soon, I think FF will become a larger part of companies profits as the lower end of the market is squeezed harder for price but ASPC will likely remain the larger market. The difference in sensor price becoming insignificant still seems along way away and you'd still be left with the difference in lens size/price.
You look at Reinz vacation setup for example, just a 50mm and 85mm lens is not something I see most people who are "really into" photography being happy with. Personally I'd want coverage at least from 16mm-200mm and possible longer depending on where I was visiting, likely some of it fast.
With the setup I look to La Palma a few weeks ago for example my D800 was only a small part of the weight, Nikon 16-35mm VR, Tamron 24-70mm VC, Nikon 80-200mm, Nikon 50mm 1.8. That's roughly 2.5 kg in lenses(not to mention the tripod and filters) that I wouldn't expect to be any smaller with a mirrorless system which most of them wouldn't balance on well anyway.