How big is your printer? I print 16x24 off an X-T1 very easily, even on high detail subjects, and I can often get away with 24x36 at very high quality, although the X-Pro 2 I have on order will be more comfortable at 24x36 than its little brother is. From everything I've seen in early reviews, there is NO question that an X-Pro 2 will be comfortable at 24x36" (the limit of my printer) on pretty much any subject, looking at the print closely. It will also have dynamic range and noise characteristics equal to the A7rII (it won't have the resolution, of course).
An X-Pro 2 (or the X-T2 that is soon to follow, if you like that body better) will be MUCH cheaper than replacing eight really nice Fujinons with Sony/Zeiss lenses. Depending on which Fujinons you have, there are probably some of them you can't replace at any cost without going for adapted lenses.
Many people like adapters, especially on the A7rII (which at least maintains full autofocus performance), but I've always personally been more comfortable keeping as few pieces on the camera as I can... There IS finally a name-brand (Sigma) Canon lens to FE body adapter, which is certainly better than something sold only on eBay. I can't tell from the one picture on the web if it maintains weathersealing or not...
I'd keep your Fuji gear (and add a 24 MP body if you want more resolution) UNLESS:
1.) You have a 44" printer the size of a piano and routinely print larger than 24x36" - there's no denying the extra resolution will help there (or you have a 24" printer and routinely print 24x50" panoramas or the like from a single frame).
OR
2.) You are routinely shooting the (tack-sharp) Fujinon 100-400 at 400mm and STILL having to crop to get your composition, and you know what you're going to do for a 600mm lens on the Sony.
OR.
3.)You have a specific fast Sony or adapted lens in mind that provides bokeh you just can't get on APS-C. Perhaps the most obvious candidate is the 35mm f1.4 Distagon ( equivalent bokeh on a Fuji would require a 23mm ~f1.0, which doesn't exist). The Fujinon 56mm f1.2 is awfully close to the new 85mm G-Master (half a stop), and the APD version should provide the half stop of improvement. The other candidate, of course, is a Noctilux on a Leica M adapter (the fastest Sony or Zeiss normal lens in FE mount is the 55mm f1.8, and the Fujinon 35 mm f1.4 is very close to that, not to mention the rumored 33mm f1.0).
Apart from those specialized circumstances (or video - but wait and see what the X-T2 has up its sleeve - Fuji execs have been hinting heavily about that one, and their new processor is MUCH faster than it needs to be unless they're heading for video or medium format), the Fuji system will do what the Sony will, and not only will you save a ton of money, you'll have a very familiar system where everything is beautifully built and works the same way. Sony is making huge strides, but at least to me, their cameras still feel computer-ish.
