If you want to go to more MP I've heard the A7R is a fine choice. Talking to friends about it, the limiting factor seems to be the choice of lenses and the necessity to really nail the camera down on a good tripod to maximise the potential of the system..
The tripod-mounting is quite normal for me, in fact I never attempt a freehand shot, except trial random shots. ALWAYS shoot on medium-sturdy Tripod.
But the most limiting factor I found with A7r is the limitation of lenses with Sony. No Sony lenses are in the 'Best' category, no blame, lens is no kidding, at least they make great strides in camera tech.
So one has to depend on third party lenses: and best of them are spread among many brands, all having specific mount measures. (I will say it is high time to agree on a single spec. mount to all cameras/lenses.)
Here enter Adapters: None is perfect. Wonder why no serious entrepreneur entered into it. Short, the great image created by best camera+top lens combination is ruined by a stupid piece of metal in between them
I plan to buy the A7r+ Canon 24Tse+ Tripod is a currently best combination for best digital image. But no adapter available in world something near to it in quality and compatibility.
(See the story: http://blog.kasson.com/?p=4024
I am really worried, if my money is ruined or not.
I've gone to a smaller system (Fuji) for reasons of weight, and I don't make prints over 24" wide, and it's fine for that. But I have to say that the 5D2 with Magic Lantern loaded was a formidable combination, though the 24-105 was not really up to scratch as far as sharpness went. I used an old Contax/Zeiss 35-70 with an adapter when I wanted sharp.
Here's another possibility. Your 24 and 35mm lenses are the sharpest? Have you thought of sticking with those and trying up-rezzing? The learning curve for the software may be a lot less than that for mastering a new camera, and some folks say they can't see much difference. I've tried a couple of products, but though the results were good, they were no better than the on-the-fly uprezzing and sharpening algorithms in Qimage so I abandoned the idea and saved myself the larger file sizes.
I studied many such 'image enhancing software' short-cuts: Not satisfied so far. They are all good to make SOME improvement in size, de-speckle, sharpen.... but all are good if the need is for a medium quality.
When enlarging the limitations show up.
At any rate, changing systems is a fairly major step. Can you borrow a Sony and see if the ergonomics and output suits you?
Yes, it is costly, new training, time waste: but no way to stay in the race in terms of technology, and demands. No other way.