Since the 3880, 4880, etc. the new x900 line-up uses the HDR inkset with two its new inks. Epson has said that they cannot make a 3900 because the printhead would be too big. So what are the possibilities?
1. They could do a 3885 minor upgrade using the 3880's K3 Vivid inkset, but that would be a hard sell. (20% faster? 15% smaller? I'll pass.)
2. They could be developing a specialized minor tweak on the Vivid inkset, still with only 9 channels, but with increased gamut. Call it UltraChrome K3 Extra-Vivid. Given that no one can see any significant advantage to the 11 channel HDR inskset, I don't see this possibility as a concern to 3880 owners.
3. It's always possible that Epson is working on an entirely new inkset -- not even in the UltraChrome family -- that goes back to fewer cartridges or in some other way makes a significant 3880 replacement possible. Such a development could happen at any time, but to release it now would piss off all the people who have sunk big bucks in the x900 series not so long ago.
I and lots of other people have upgraded from 3800 to 3880 recently after fretting over this issue, so if a major 3880 replacement does in fact appear any time soon, you'll have a lot of company in your buyer's remorse. But Sal makes a great point. Even if the hypothetical replacement were announced tomorrow, it could still be two-three years before we'd have a realistic appraisal of its issues. Some problems simply take that long to manifest.
(Interesting to speculate on what Epson does next to make a really meaningful upgrade to it's UltraChrome K3 inkset. As user Enduser mused in a recent thread, wouldn't an archival dye inkset be wonderful? No clogs and really deep blacks. (But of course there were other problems with dye inks besides longevity.) Mere increases in gamut seem not to be that compelling for people who don't routinely photograph neon tetras. Greater Dmax on existing papers would be an easy sell. But the real El Dorado for me would be a major boost in longevity. Can't recall his name, but the guy who does alternate longevity testing to Wilhelm institute makes a compelling case that Epson's yellow pigment is UltraChrome's Achille's heel. Trouble is, it already takes years to do accelerated aging tests, so presumably they'd have to have hit on the right formula four or five years ago in order to have meaningful evidence of success for a product launch today.)