The recent security Update to WP 5.0.1 also brough an update with Version 4 to 4.9.9.
I got a clients project which where build on swamp land ages ago. Every Update is Hoping nothing will happen.
Now i do think of staying with WordPress 4 for my maintained nightmare project, if they still develop important security updates.
There is also the classic editor Plugin, which isn't working for every case. Got already another Project where an very old unmaintained Plugin get unusable. I do fear even interrupting changes with placing the classic editor. It's a quite big page and i guess my client isn't willing easily to pay a refactoring which needs several weeks on programming. Of course i can test everything on a testing system..
But of course it won't be a comfortable click of a button to update. I will need to go with SVN or GitHub i guess.