There are printers that apply a 'clear coat' of something to kill the differential, no??
I think you're referring to what Epson calls gloss optimizer and Canon calls chroma optimizer. Among current and recent models, I think the Epson R2000 and P400 and the Canon Pro-1, Pro-10, and Pro-1000 have it.
Any improvements lately in dye based printers/inks..longevity issues..fading issues due to humidity or light etc?
The Canon Pro-100 supposedly makes long-lasting prints (only) when using Canon ChromaLife inks on several different Canon papers. The estimates seem to be that such prints are likely to last at least as well as, and probably better than, good conventional wet prints (RA-4 process on Fuji Chrystal Archive paper).