Ya, 8K is something I would feel concerned to go after for a while... HDMI 2.1 overall, though, is potentially an important upgrade if you need 4K 120Hz for gaming for example.
Sadly, 2.1 is a mess, and the new Yammies don't even support fully operational 2.1 out of the box, rather pending a firmware update sometime "this fall."
Also, Gene says he found some troubling behavior while benching the A6A and is in conversation with Yamaha about what was happening.
This is, frankly, a bad time to be buying electronics.
If you have to, you have to...
Depending on your finances, going after something to just get you by until the technology and availability problems are solved could be wise. A placeholder Denon 3700, for example, even refurbished, may be a compromise solution. Though not without it's own hdmi 2.1 baggage, if you aren't a gamer, it shouldn't be a problem.
*shrugs