Thanks for answering, Matt! Yes, I'm hoping for a LTS.
Updating the codebase with incremental updates would be fine, the problem is the course itself (record and edit videos). A single video can take a whole week - imagine a full course, and then a week later a breaking change of Godot 4.whatever breaks 3 videos.
That's why I'm being careful, I also the course version for v4 to be long-lasting, just like the current version of the course is already definite for 3.5 and won't be deprecated.
I posted this via the course newsletter too, so I already have a few answers and opinions I got by email, I'll wait a week, and soon I'll have a decision that will be based on the average of the answers :)