As you can see from the replies, there are many options. The other day, we went to the mini photo fest held by
London Camera Exchange in Bath. I put this also in the context of having been harangued at a presentation about the wonders of one particular brand for about 40 slides and an hour.... Anyway, there was a brand ambassador there [different marque from the Death by Powerpoint presentation]. He started by saying that there weren't really any bad cameras any more. His advice:
1 - write down what you want your camera to do.
2- research and find out which cameras do that, regardless of the brand name.
3- cross out the ones on the list that you cannot afford
4 - go and get hands on the ones that are on the list.
Now, you also have the added element of having a system already which has mirrorless cameras and a much debated / argued recent release that is full frame.
In terms of mirrorless experience myself, I have tried a few. Personally, I like the look of the Olympus system and I was able to try that before I bought - Olympus WOW. It's a much lighter thing. Can it do everything that my Canon FF does? Well, I have seen some terrific results from the Olympus ambassadors like Scott Bourne but I am not there yet but I do know that it can be done. It produced two of the images in my monochrome panel for my ARPS recently - two that I wouldn't have had if I hadn't taken it on walkabout down at the beach in Oz.
Good luck with your decision.