In the LF forum we discussed a bit scanning backs. Of course they have disadvantages, but with modern technology, and will there could be somebody making a modern scanning back, 4x5 or bigger, high resolution.Even if have large sensor, as far as I know there are no lenses, or even a lens line, in production anymore. Use old film lenses?
I kept my 4x5" gear now for decades, hoping that eventually there will be a 4x5" digital sensor. I would be happy with measly 24MB but I am giving up on that.