In short, there are two pending issues:
- Java 8 lambdas in Scala 2.12 breaks the Dataset API: more details
- they need to remove a method = requires major number bump (ex: 2.2 to 2.3)
- this is from March 2016
- this is solved / trivial
- Closure cleaning for Scala 2.12: 1% of tests still fails (2 tests) more details
- PR fixing 99% in November 2017
- remaining 1% is a hard problem, they might cut a release anyway
My guess is that it might be available in 2.3. The version 2.2 was released the 1st of December 2017. I would say this will happen in 2018 
.