JDK17 is last LTS release of Java platform. It is bringing many cool improvements - http://openjdk.java.net/projects/jdk/17/ and is landing to your Fedora. Where it will be maintained for several years. You will always be allowed to install Used LTSs in build root, and alongside via alternatives.
See announcement: http://mail.openjdk.java.net/pipermail/discuss/2017-September/004281.html
See java SIG plans: https://jvanek.fedorapeople.org/devconf/2018/changesInjavaReleaseProcess.pdf