I heard from a mod of a large sub that old.reddit is not going anywhere - apparently all of the admin tools are built on old.reddit, so shutting it down would not be feasible without a huge engineering effort.
OTOH, I've already stopped posting and commenting and will only resume once they change their stance on moderation tools and third-party access. If old.reddit goes for good, I'll go as well.
I realized they are making it worse and worse to use for mobile, like the browser version barely works anymore on mobile, and sometimes forces you to go to the app :(