After April 30, 2019, Adobe will no longer provide any updates for CF11, so there will be no security patches or hot fixes for CF 11 after that. Of course, updates for CF2016 will indeed continue into Feb 2021, while CF2018 updates will continue into July 2023. And we could expect CF2020 (when it comes) to by supported into 2025.
How do I know this? Where does Adobe say it? And can one buy support (yes) to "buy extra time to get such CF11 updates beyond April" (no)? And what about CF11 support for Java 11 (no)? Finally, could you use help in moving off CF11 to CF 2016 or 2018? For more on each of these, read on.
(Update: I should note that Adobe did indeed offer one more update beyond April 2019, in June, when they updated CF2018 and 2016 as well for an important security update. That was a bonus. They have said there really will be no more CF11 updates, as per the original plan.)