User blog comment:MisterWoodhouse/Fandom is upgrading to a modern version of MediaWiki/@comment-38722340-20190626064354/@comment-3020860-20190630011803

As SeñorWoodhouse indicated this will take an unknown amount of time to happen, so it's hard to say where MediaWiki will be at whenever it finally does. But I certainly hope they wouldn't consider moving to anything earlier than (as of today) MW 1.32.2 [current stable] or MW 1.31.2 [current LTS]. Starting this upgrade off with a backrev version of MediaWiki would just be setting themselves up for a repeat of the past 10 years.

Ideally, the outcome of this upgrade would be a MediaWiki install that they can upgrade regularly, keeping up with new versions as they're released, without the whole house of cards collapsing in the process. They've got to separate out and cleanly compartmentalize all the "Wikia stuff" first, in order for that to be a reality, but it sounds like that's exactly the plan. A clean architecture would see Wikia's mods applied on top of MediaWiki using the built-in customization hooks (which are extensive), so they're able  to be migrated from version to version.