Part of "Digital", the lowest level of digital, is a contract concerning how signalling between transistors occurs. This includes timing, rise and hold times, voltage thresholds and current. I'll include avoidance of race conditions, clock distribution, refresh cycles on DRAM and temperature effects as a side car. These are all design constraints that make sure the 1s and 0s working properly. It's only when you have a 99.99999999% solid digital contract that you can begin the digital side of the design.
All of this digital design is solidly analog and will NEVER go away.
I could make another whole post about the absurdity of traditional "analog" going away. All these mobile devices have some amazing RF design going on from the antenna down to the mixed signal SoC. Analog is everywhere and at the core of every electronic gadget.