According to Digitimes, the mass manufacturing of the PS4 Pro is already under way. The process is in the hands of Foxconn Electronics and Pegatron, but it seems Sony's new console isn't the only gaming device in their hands. The same site refers to "industry sources" that have claimed that production tests for the Nintendo NX have already began.
With the launch of PS4 Pro scheduled for November, it will be interesting to see how what kind of supply and demand awaits the new version of the PS4. As for Nintendo NX, it should arrive in March 2017.