On a recent thread (
https://www.bikeforums.net/bicycle-m...ad-triple.html )
under reply #8 there was mention that Shimano's latest 11 spd cassette, the 8000 series Ultegra 11-34 is back compatible with 10 spd hubs
sort of like the 11 spd MTB cassettes being compatible with 10 spd hubs. Researching this gave some incomplete data but may
be worth exploring, as a way to keep your present wheelset (ie some Shimano sites show no 11-34 11spd, others do but no other info).
An 11-sp cassette (eg. CS-R8000) can't be used on a 10sp hub because the freehub body is not wide enough. On the other hand, a 11sp freehub can accept a 10sp cassette by adding a spacer. I don't know why anyone would want this option but it's possible. If you go to the Shimano website, you'll that the Ultegra freehub is listed as 10/11sp, but the cassette is only listed as 11sp. Here's the link:
FH-6800