No official confirmation (yet), but Nikon may be migrating to a paid firmware update model. This post on Nikon Rumors has more detail, but the first reported features are:
The “I Am Advancing” program is starting with support for 6 full-frame Nikon DSLR cameras: Nikon D750, D810, D800, D800E, D610 and D600. All of the cameras in the program will receive a new White Balance update, containing Nikon’s latest algorithms for high-quality color balance in any light. Each camera is also receiving a brand new “Metallic” Picture Control option, providing photographers with a unique high-contrast setting which is both natural and eye-catching.
For photographers using Nikon RAW (NEF) mode, the most exciting new feature is Nikon’s new RAW Histogram. This feature displays impressive full-screen histograms for all 3 color channels (red, green and blue) simultaneously, based on data directly from the image sensor. The new feature allows advanced photographers to fine-tune perfect exposure for each shot. RAW Histogram is available for all cameras in the “I AM Advancing” program.
Finally, Nikon is bringing 2 of the best features of the revolutionary Nikon D810 camera to other cameras in the Nikon DSLR line-up. Nikon’s new “Flat” Picture Control, which allows photographers more options for adjustment in post-processing, is now available for all cameras in the program. In addition, Nikon’s Electronic First-Curtain Shutter feature, which eliminates vibrations caused by the shutter, is newly available for the recently announced Nikon D750 camera.
After Adobe's [financial] success with Creative Cloud, more companies are looking at the software subscription model as a means of generating recurring revenue. Sounds like Nikon is dipping its corporate toe in the water.