It may be that nobody would choose XML as the base for their new standard. But there are a ton of existing standards built around XML that are widely used and important today. RSS, GPX, XMPP, XBRL, XSLT, etc. These things aren't being replaced with JSON-based open standards. If they die, we will likely be left without any usable open standards in their respective niches.

Looking at the list, what actually jumps out at me is there is probably a gap in the world of standards for a JSON-based replacement to RSS. Looking it up someone came up with the idea of https://www.jsonfeed.org/ and hopefully it gains traction.

In hindsight, it is hard to imagine a JSON-based RSS-style standard struggling to catch. The first project every aspiring JS developer would be doing is how to add a feed to their website.