Long term though it's not just about the resolution.
HDR is a noticeable difference, so anyone with a 4K HDR compatible TV will get a quality bump over both SD and HD when HDR is standard across all 4K broadcasts.
But getting HDR to be included is the current technical challenge faced by all broadcasters. That's why the BBC trial during the summer wasn't just about 4K's bandwidth requirements, but also (and mainly) about how well HLG HDR would work.
It's not been completely settled how HDR will work in the DVB standard either -
https://www.digitaltveurope.com/2017...adata-for-hdr/
Even if it has been sorted since the above was written, it will take time for all playout technology to be updated to copy with HDR standards.