Nvidia is looking for new applicants who can "help produce the next revolutionary Apple products."
http://www.notebookcheck.net/Apple-may-be-returning-to-Nvidia-graphics-for-future-Mac-products.178595.0.html
Although that would be great, the current generation of AMD video cards in the MacBook Pro 15' model is the R9 M370X which I believe to be only a 50 watt model. Currently Nvidia only announced the GTX1060/70/80 models which are 90 watts and above. Seeing Apple leap towards thinner products and not performance gains, I think it's safe to assume the more powerful models of graphic cards will cause a lot of heat dissipation problems.