In an alternative reality were DotNet never happened and MS evolved Win32API with COM (so basically continue the strategy of 1989-1998 until the great break with DotNet happened), yes then a new "Win64API" with modern C++ would have been great. But the Web happened, DotNet original vision failed, their pivoted vision was declared as legacy 5 days ago too, and UWP failed with no one buying their Win10phone (0.02% global market share).
