Existing concurrent licenses could fail (ie be unable support latest release of Pro) sooner than 2026. The "10.1 - 10.8" block of ArcMap concurrent license that also licenses up to latest (currently 3.3) Pro may only go so far, and is the last version of Desktop license that we'll see. (just as the prior license block for 10.0 only went "so far" (edited, bc version correlation may have been wrong, but those details aren't important))
For example, upon the release of "Pro 4.0" (could be even earlier, whatever version cut-off they choose) it seems reasonable to expect that ALL former "you get Pro with Desktop" licensing would fail - because there's no more Desktop concurrent licensing AT ALL* as of 7/1/2024 (e.g. don't expect a "Desktop 10.9" license that includes "Pro 4.0"). I get that, we all know Desktop is going away, and has been expected, but they're closing doors on existing licenses in other ways sooner than expected.
*That also means existing licenses can't be upgraded either - which is how I learned about all of this in the first place, while attempting to upgrade a Desktop+Pro from basic to advanced. I did literally ask regarding a supposedly "grandfathered" concurrent license, and was told that the ONLY WAY forward was to acquire a Prof+ named license.