When will deprecation of VSTO and COM add-ins happen to Word/Excel/PowerPoint?

Question

I understand that the New Outlook has stopped supporting VSTO and COM.

Seems I need to plan for a roadmap to migrate all office add-ins to JavaScript, however I found there are some important features like custom open/save locations, making documents readonly are missing in the JS version.

I would lile some advice on when I should start the migration and how to substitue the missing features.

Thanks