George,
As you know, I'm moved by your work. It's all possible because of your own past, present and drive to make impressive images expressing your unique view of your world. Until now, these strengths plus inspiration and support by your lovely wife have yield for you coherent sets of pictures of worth. That itself is a stellar achievement and one you'd have done no worse with many lesser cameras.
New cameras desire is mostly the construction of memic "needs" created by our online communities and clever marketing that don't reflect any functional necessity, just razzle-dazzle. It's a self-delusion that we buy into so readily as the gadgets do in fact all come with new glamorous features that are so seductive.
Of course the new one does better in low light, but that is not really a block to creativity, just nice to have, but you are not a rich dentist, LOL, and likely as not money is a commodity that does not just flow into your Paris apartment. So let me address you as if you were in my own family.
You also have so recently expressed your frustration at the high, almost impossible barriers to getting to the "Art" market place and complained rightly at the self-serving nature of so-called open art "competitions"! So, being older, with many more disappointments and more than a few successes, I look at your angst for a better camera, with a filter of age. I've the benefit of many more mistakes and bubbles of delusion than you have under my belt! With that, I can't help but feel that saving money until you find you can no longer get the work done, would be wiser. If you were blocked in getting/completing the paid assignments you are offered then, of course, you get the camera!
Alternatively, Mark's idea of using film does give you both a tactile, pacing, esthetic and marketing self-branding that could move your work to a new level. Look at Dawid Loubser's journey in this forum doing exactly that!
Asher