In reply to Rick Gregory.

at some point, we need to either redo their site to work in WP 5.x (or 6.x) *IF* possible
I do not think that it would be a viable option as all the cons reported by the community seem to be neglected. Why would this change later?

Responsible devs who are building WP sites for real clients simply can not afford that level of uncertainity that is coming because of the Gutenberg project. Luckily in the last year i only had 1 WP project as i moved to another CMS earlier. Stopping updates at 4.9 for my old clients sounds a good idea, that's what i will do as well.