8K is four times the pixels and therefore four times the bandwidth as a 4K monitor.
It took us a long time to go from 1080p to 4K. It has taken even longer for 4K at 120-144Hz to be practical.
It’s more likely that you’ll end up with intermediate steps to 5K, 6K, than getting 8K 120Hz.
The other limitation is lack of demand. You need a gigantic monitor for 8K to be worth it, and you need a powerful video card to drive it. The number of people who would buy such a monitor is very, very small.