I can easily believe the results of pixel-shifting, at its best, rival the current state of ~50MP crop-645 capture. The idea of super-resolution has been around for awhile. Aside from the few cameras supporting sensor pixel-shift, super-resolution has been mostly a multi-frame technique blending multiple shots with desktop software. Putting it in the camera is simply an extension of the technique that can also take advantage of in-camera reduction of de-mosaicing issues. A Foveon type result working around the Bayer array, if you will. I don't think there's any doubt that Foveon images can be enlarged beyond the level possible with Bayer images, and enjoy greater tonal and colour resolution than Bayer images.
Unfortunately, super-resolution suffers from the same limitations as do other multi-frame techniques like stitching, depth of field frame stacking, and HDR -- for best results it requires largely static scenes. And there's always potential manual frame blending & retouching work to fix stuff the software couldn't handle automatically.
I prefer the look of the larger sensor & optical platform of 645. (And would shoot even larger if it was feasible to do so in digital, in a cost-effective way.) But if & when super-resolution comes to 645, I'll happily use it in the situations where it can work. Same as I do with stitching, DOF stacking and HDR, all of which I employ when needed to augment the camera's limits.
It remains that, for my purposes, a K1 (or virtually any other 35mm system) still wouldn't be close enough to my 645Z in enough circumstances to be considered a "backup". For me, a backup system is one that lets me keep doing my main work, how & for the purposes I want to do it, if a primary piece of kit goes down. For me that means my current benchmark is a 645 digital system. Of course others will make that trade-off decision differently. Which is why these threads usually are challenged in providing "answers" to an OP... it's all subjective. What's right for one person is useless for another. Mainly we can share what we've personally chosen & why, and perhaps the OP can glean some decision criteria from that...