From system point of view there wouldn't be any complications with different hardware combinations. Linux handled the multi-core transition seemlessly, I have no doubt it will handle the Phonebloks too. However I think that there is a way to go for the Apps and the android.

I have come across that small/mid-sized companies usually look for a drop-in replacement of the leaving employee. Sometimes they even ask leaving guy to write the list of capabilities and technologies. Since the technologies and tasks are changing with time and from project to project, resulting job description defines noone but the leaving guy. Once, the company I had worked for, advertised a software engineer who was capable of programming dotNet and VHDL at the same time. In Turkey, a usual hardware developer position includes hardware design + firmware development + PCB design. (P.S. with my limited knowledge from Turkey and Europe)