This has been a long time coming; the Trac ticket #37110 is already few years old.
Following the recommendations of the jQuery team, the updating has to happen in stages:
Remove jQuery Migrate 1.x. This is planned for WordPress 5.5. Update to the latest version of jQuery and add the latest jQuery Migrate. This is tentatively planned for WordPress 5.6 depending on test results. Updating to the latest jQuery UI, version 1.12.1, is also planned for 5.6. Remove jQuery Migrate. This is tentatively planned for WordPress 5.7 or later, depending on testing.
As planned, a Test jQuery Updates plugin