I still has not decided after a lot of advice, after reading a lot of posts on various forums and watching a few videos on youtube im not so sure. I wont use any new features like wifi and gps and i dont care about the touch screen at all and i wont film or even use the auto focus. The upgrade for me is more about noise but its very rare that i go over iso 200 on my mkiii. Will i see any diffrence in noise levels on low isos like 100-200? The second thing is the dynamic range and details in the photos. It would be nice to get rid of the chromatic aberration completely in landscapes. But will the diffrence be that big? Thas the two thing i cant find in the tests. Sure, the extra pixles would be great but i dont really print for myself. I only use the camera for stock photos.
Chromatic aberration is a lens issue, not a camera issue. Canon 5d Mark III already has a chromatic aberration correction available, maybe the mark IV pushes the correction a little more, however I don't think it does something that you cannot do in a post processing software.
Usually, photographers skip a generation when upgrading, because that's when the difference between models becomes visible. So, from 5d Mark II to IV - definitely worth an upgrade. From III to IV... not so much (at least not for the usage you have described).
Anyway, remember it's a lens issue, so if you want to see a difference, buy better lenses before upgrading the body.