Sony isn't getting rid of discs because of the limitations of the technology - otherwise, they would be R &D ing higher capacity blu-rays (or maybe something else). They're doing it because most gamers are now digital so don't want physical, and also because they want more control over selling games themselves. So, all of these suggestions for cartridges or whatever seem entirely to be missing the point.
Physical media is evolving, even if future PlayStation consoles only support digital games. A British tech guru believes Sony should consider small 3D NAND flash cartridges. This fast, removable storage is expensive at higher capacities, but would address complaints from collectors.