So OK I am a bit late to the party here, but I will play the Nikon fanboy/troll anyway.
You could go out and buy a nice used Nikon D800E, and, 14mm to 24mm F2.8 to go with and still be in under budget for the 5DMkIV body alone, that is if you are seriously concerned about IQ/dynamic range/sensor performance. My feeling is the D800E or D810A are likely as good as and possibly better landscape sensors than any of the sensors available in any Cannon body even the 5DS R body with 50 MP sensor. The 5D sensor does seem to be a better sensor than the 7D by a good bit, just not as good as can be had, particularly for dynamic range at typical landscape ISO’s.
What size images do you typically produce? If you are not routinely producing images on paper/canvas larger than say 24”x36”, I can’t see any significant need to change sensors/spend money on the latest and greatest from Cannon or anyone else, unless there are some other bells and whistles the body has you just can’t live without. So, do you routinely produce, or intend somewhere down the road to produce printed images say 40”x60” or larger? If so, then I’d say you likely need a better/larger sensor to do the job justice. Further if this is the case, I’d say forget Cannon and go Nikon if you want to stay in full frame 35mm land or there is always one of the ultra-high dollar medium format cameras if you see billboard size fine art prints in your future.
As someone has already succulently put it, the photos you post here are not lacking, nor those on your web site. Of course if you just want to buy a nice new toy with nice new shiny bells and whistles, well that is sure OK too, that is what makes the world go around. God knows I’ve done that a time or two in my life and not felt the least regret in the doing. I am sure that many here have and will help with a multitude of rationalizations to help you pull/not pull the trigger on that purchase.
So bottom line, for me, lots of giant sized physical prints, go for a larger better sensor of whatever stripe or verity suites your fancy, I say Nikon, otherwise keep what you have and spend the coin elsewhere.