The TL;DR is that Red Hat and IBM are going to take over from Oracle as primary maintainers of java 8 (in the form of openjdk) after January 2019. That is likely to last through at least 2022.

Going forward Oracle will be primary maintainers of openjdk for each new version of java for six months. Every third version (starting with 11) the hope and expectation is that RH, IBM, et al will take over after those six months are up and continue to support those versions for at least several years.