The logical successor is Drupal 8, released in November 2015, and has a slightly different 'release cycle' from previous versions: where Drupal 8 is an almost completely new version compared to Drupal 7, and therefore can be quite some work to migrate, Drupal 8 is being set up in such a way that migration to Drupal 9 will be a much smaller step; the first version of Drupal 9 will therefore be a minor upgrade from the latest version of Drupal 8.
I now have a Drupal 7 website. Do I have to migrate? And if so, how?
When the End of Life enters, it does not mean that the website will suddenly stop working. From that moment on, it solely means the Drupal Association does not provide official support, and therefore will no longer be active development on the platform, and there will be no more security releases. In all likelihood however, there will be a paid service for official support, just like this was the case with Drupal 6. In addition, there will always be a community that may pick up on development. In other words: the development will not come to a complete halt.
Our advice, however, is to think about taking steps for a migration, especially when there are concrete plans now for (relatively large) updates. Keep in mind, however, that a migration is primarily a migration of content. Functional components may have to be redesigned and reimplemented. A new theme will need to be developed, as old themes will not be able to be migrated. This therefore offers opportunities to update your site and bring it into the next century :-)
Should I not wait for Drupal 9?
Drupal 8 will be phased out at the same time as Drupal 7, so it may feel a little illogical to go to Drupal 8 first. But this is precisely the advantage of the setup of Drupal 8: the code is written in such a way that Drupal 9 will continue where Drupal 8 will stop, without having to do another complete migration. Read more about the Drupal 9 plan in this article.