It's mainstream for new projects. Which is what was expected and aimed for.

Citation needed. Most companies I know that have 2.7 older projects also do new projects in 2.7. They don't want to introduce 2 different versions of the language, set of dependencies etc to their production.

absolutely true. imagine porting a decade or more of code for only the promised benefit of a more "pure" language. asyncio is nice, but excluding it and enhanced generator syntax from 2.7+ is >policy<, not engineering. python 3 is bootheel style top-down engineering >management<, not good engineering. The BFDL is fallible. Placeholder looks like a great Python 2.8+ to me. Runs all my old code and gives me new syntax, without rejiggering the stdlib for purity's sake? Twist my arm.