APFS does work with spinning rust, and no existing disk repair and maintenance utilities will work with it; they will all have to be rewritten. That much is known.
The rest? It's anyone's guess. A limited version of APFS ships with macOS Sierra (you can format a drive APFS, but it is not a feature-complete implementation of APFS), so it's completely unknown how long it will be before it's rolled out for real in macOS. I would guess probably not the version after Sierra, but maybe the version after that.
