Python 3 was shipped with the expectation that the migration would be long. Python 3.0 was the proof-of-concept release, basically, and it wasn't really until 3

Python 3 was shipped with the expectation that the migration would be long. Python 3.0 was the proof-of-concept release, basically, and it wasn't really until 3.3 that momentum started picking up around porting. 3.5 and soon 3.6 are beginning to offer large, attractive new features people want and can't get on 2.7, which further incentivizes the move. But in order to make it happen, and to provide the long lead time for migration, 3.0 had to get out the door when it did. So it wasn't "premature".