This Wiki has yet to come to any kind of decision as to what we'll do when FANDOM forces us to retire the Forum and moves its contents to Discussions.
However, I am of the opinion that it would be much, much, much wiser for us to return to the old wiki-style Forum (you know, like those), as far as serious discussions for creation of policy are concerned. In my capacity as Wikimaster of a different Wiki, I contacted FANDOM Staff to make sure that this was possible, and they confirmed that it would take a simple request for them to unarchive the old "talk-page-like" forums.
The Discussions app may be of easier access to casual mobile users, but it is incomparably worse for serious discussions where you want to be able to post long messages with complex formatting, several images interwoven with the text, test out templates, etc. We couldn't possibly have something like Thread:267362 in Discussions unless Staff fundamentally change the workings of Discussions in ways they never said they would.
It is flat-out not possible to write even halfway-complex template code in a Discussions post, and that alone should condemn Discussions to remain what it is — a place for users to chat more casually about Doctor Who, rather than have rational and structured discussions about Wiki policy.