With the advent of the Project Update Bot, we have a much more reliable place to link people to. "Plans" are a field on projects that maintainers may fill in. I did a quick API-based check and of the top 3500 projects, only 600is filled in their plans. When Drupal 10 was about to be released, the old Drupal 9 plans were wiped out in favour of Drupal 10 plans. Now Drupal 11 is coming, but the Drupal 10 plans are still in place. While this seemed to be a good idea originally, it turned out to not be a very effective way to disseminate plans. Deprecation status removed plan support (gathering and display) earlier already.
Remove plan support from Upgrade Status.
Fixed
4.0
Code
Issue #3432351 by Gábor Hojtsy: Remove plan support (download/display)...
Automatically closed - issue fixed for 2 weeks with no activity.