3.7 it's a minor update from 3.6, that basically consists in changes to the standard library rather than the language, and 3.8 I think it will be the same, so once the 3.6 support is implemented it will take less time to implement 3.7 support.
Dataclasses are a sweet feature that I can see getting wide adoption pretty quickly. This said, they have a backport and it's mostly just sugar, so I expect one could probably get them working on 3.6 pypy.
