The problem with supporting APFS and HFS+ at the same time is that FileVault and Time Machine need to be very different on APFS. FileVault can take advantage o

The problem with supporting APFS and HFS+ at the same time is that FileVault and Time Machine need to be very different on APFS. FileVault can take advantage of the transparent encryption feature of APFS and TimeMachine can simply backup a snapshot of the file system. I don't know if Apple (who likes to drop things) will support both concepts. Also the reason why I assume that APFS will be coming to macOS in the next major release and not in a point release.