I use a Canon 5D2. I usually use it on a tripod set to iso 100 and stitch exposures using a tilt and shift lens. I produce large prints (24 x 30 and larger). Stitching isn't always an option so I was hoping to eventually purchase a Medium Format system but I don't think that is going to be possible ($$$). Instead, I'm considering purchasing a high pixel count FF body (in lieu of a MF system). I'm tired of hoping that Canon will announce a new high resolution FF camera so I'm considering a Sony A7r body. I would keep my Canon and Zeiss lenses and use them via a Metabones adapter. Has anyone out there done this? If so, I'd like to know how it's working out for you.
I'm in the same boat as you--5D2,zeiss & leica lenses.
My close friend just got the Sony,and he loves it,with the exception of the menu set up
After he had it 1 month,I asked him.."is there a big difference between the 5D2 & the new Sony"?...his answer was yes
Then 4 weeks went by ,& I asked him the same question ,..answer--"kind off,somewhat"
My feeling now is,unless there is a major,night & day increase in image quality...I'll stay put.
Good luck with your decision,
Mike