Recently I have been planning ahead with a couple of clients for their Drupal 7 upgrade. Drupal 7 will be supported by the community until the end of November 2021.
What does this mean for Drupal 7 projects? It means that if you haven't started planning an upgrade to Drupal 8, you should now.
The same goes for Drupal 8 and Drupal 8 will only be supported to the end of 2021 like Drupal 7, but the transition will be very easy to Drupal 9. That means by the end of 2021 each Drupal 7 and Drupal 8 project should be updated to the latest version of Drupal 8.