Apple released several updates for it in the past year containing a lot of changes, indicating that development is active. Do you have information suggesting otherwise?

I'm in the same boat as OP, as I absolutely love Logic's built-in software synths and composition-friendly UX.

Care to elaborate as why you think Logic is a long-term mistake? You think Apple is transitioning away from support?

I think locking yourself into any single proprietary format is a mistake. I realize my comment came off as implying Logic is doomed, but if you're really worried about vendor lockin, spending an afternoon on tutorials and a few side projects in the new environment can really help build your skills, not just in the new toolset but in the old one as well.