macOS Sierra compatible with classic Mac Pro

macOS Sierra and the Classic Mac Pro: Early reports suggest full compatibility with 2009/10/12 5,1 systems

As the title states, Apple latest OS (macOS Sierra), seems to be fully compatible with any classic Mac Pro bearing the 5,1 identifier. 2009 Mac Pro 4,1s are out, but those upgraded to 5,1 firmware seem to work fine.
For anyone out of the loop, Apple announced the latest incarnation of OS X 10, renamed macOS, at WWDC last night. Check the video below for all of the major announcements: