This is a problem that goes beyond Fleet, it's a matter of merging all the things that are new in Android Studio back into the Android plugin for IntelliJ IDEA, which is a huge and complicated process. Once it's merged into IDEA, Fleet gets that same support as well.
We are very aware of this version lag being annoying, and we're actively looking at ways of making these merges faster. The work is currently ongoing to merge Koala, and the results of that should be available around the end of the month.
Can't promise anything specific for the timeline of merges in future releases, but it's supposed to get better over time.