If you become comfortable with annotation heavy code bases, what is the likelihood it will change in the future and you have to start over with a new style of codebases?

If there's a major shift in those languages (vs. JavaScript) it seems more worth it to retrain once it's solidified and you see companies actually looking for those skills.

Fast moving ecosystems means more things become deprecated more quickly and you also risk more "train thing that will be useless next year".