I'm expecting to emigrate in the near future with the intention of owning not-much more than would fit in a rucksack. This of course would necessitate the sale and replacement of much of my photography gear - I've got chunky stuff - 1DSIII and a range of 'L' lenses. I can see that going mirrorless may be the most suitable compromise but what of lenses?
Assuming it is a fact that my 'L' lenses are too big and heavy for my plans, what manufacturer/system should I be looking at that offers lenses with an optical quality as close as possible to my Canon L's? I appreciate that I'll be making a compromise, but what would be the smallest compromise I can make in order to save vastly on weight/size whilst losing as little as possible in image quality?
...I know this is a Canon forum, but I'm entirely open to a solution of another manufacturer!
Although I cannot comment on what would work for your personal needs, I can tell you what has worked for me ... I shoot Canon, Nikon & Sony systems (for a very long time Canon gear has been my go to system), but for the past 6 months or so, I've been shooting with Sony a7 (full frame mirrorless system) ... if you shoot only JPEG then you may not be happy with its jpeg images (Canon, according to me, has he best jpeg output of all the 3), but if you shoot RAW, then the Sony is brilliant in terms of image quality, especially how much you can post process. I use the ZEISS FE 55mm f/1.8 prime lens, which stands up very well to the "L" primes ... the ZEISS FE 24-70 f/4 is an ok zoom lens but the FE 70-200 f/4 is very good ... although I do not have the FE 35 f/2.8 lens, I did try it and it is a very sharp lens in a tiny package (so is the 24mm f/1.8 lens) ... in addition I use Sony a6000 (crop frame) for speed (shoots 11 fps ... but buffer kinda kicks in after 21 continuous shots to slow down the system, or wait for 3 seconds before you can take another 21 continuous shots at 11 fps ... but the good news is, focus accuracy is spot on) ... I now have the 10-18mm lens permanently mounted on the a6000 for 15mm-27mm fov, which gives very good results (although its a lens meant for crop frame, it does work between 12-16mm on the Sony FF a7 camera with a little vignetting (acceptable for certain ultra wide angle shots ... alternatively it can be fixed in PP).
Currently, I am able to carry 2 cameras and six lenses (plus an adapter to use my canon lenses on Sony mirrorless cameras) plus 2 speedlites in a small bag ... and its a joy to be able to carry that much gear and not feel the weight or the size. I just picked up an Sony RX100MIII yesterday and am blown away by its performance in such a tiny camera.
You may want to test the a7 and the a6000 + a few of the FE/E mount lenses at your local store and see how it works for you ... but do try out the RX100MIII it will surprise most people.