.NET Standard, the futur of .Net is here: dotnet/standard. I have great expectation of what should have be part of .Net core from the begining.
Everything happens just like when .Net 1.0 was released. A non finished version quickly followed by a short term 1.1 (mainly bug fix). Then there were many blunders around a 1.2 version, before it was abandoned in favor of a much better designed 2.0. And this 2.0 version was so succesfull that each version up to 4.6.2 have been on top. But certain inconsistencies remained (for example, BCL did not make complete transition to generics).
Let that be a lesson. A great foundation is better than compatibility to a (very?) small codebase.