Since RTB will sadly shutdown, we will need atleast a replacement for the add-ons hosting part, a website where we can upload add-ons and updates to it, including a GUI where it alerts you when an update is out so you can update it in-game or on the website just like how RTB works.
Also players can steal add-ons and builds and claim it that they made it on Steam Workshop so I don't think that will be a good replacement