As expected, Sony WANTS you to buy the digital version. They are offering the disc version for the collectors and people with no choice. The incentive is to get people to go digital and this will probably work. Even though I buy my PS4 games digitally and I already have a 4K player, I'll get the disc version just to support 4K UHD and physical media. Also, maybe we'll get lucky and they'll offer backwards compatibility with PS3/PS4 discs.
Even though I'm all digital PS4 and have a UHD player its in no ones interest for the physical market to die. That would lead to higher digital prices, lesser sales etc.