Personally, I can't see it selling anywhere near 7-10m WW. But I do expect it to sell as well as MHP2 in Japan, which is currently around 1.4m and has only been out for around 5 months or so.
Minimum, I reckon CC will do 3m WW, but it could quite easily do 4m.
Prediction (June 12th 2017)
Permanent pricedrop for both PS4 Slim and PS4 Pro in October.
PS4 Slim $249 (October 2017)
PS4 Pro $349 (October 2017)