Apple has made it clear that they intend to make APFS their primary filesystem. It seems to present many new features and advantages over HFS+.
From their APFS FAQ I see “Apple File System is optimized for Flash/SSD storage, but can also be used with traditional hard disk drives (HDD), Fusion Drives, and external, direct-attached storage.” Does this mean that it will seamlessly work with Drobo products?
At this point APFS is still in developer mode, even in the new macOS Sierra release.