It depends on how people perceive value. Having something tangible in your hands increases the perceived value. At least to me.
Myself, I would not pay the same amount for an e-book compared to a physical paper one. For games my limit is about EUR30 for digital. Above that I want physical.
If somewhere in the future Physical does not exist anymore, I don't see me buying that many full prized anymore. Max 1 a year. The rest then will be either heavily discounted or cheaper AA (Indy) games.
Perhaps I am the outlier, but if sufficient people like me exist, it's in the interest of publishers to have physical as an option to retain full prize level.