The Arduino has a huge hobbyist-level codebase and lots of libraries for talking to various devices.
The 8051 is a venerable old processor that still gets used in lots of stuff because it’s cheap, and has a low gate count.
It’s probably possible to port a lot of the Arduino stuff (everything that doesn’t use specific on-chip features) to the 8051, thus allowing people to use the software environment they are comfortable with on a new chip. The same is likely true of PICs, and other chips.
The general case, then, is to create a translation system that automates, as much as possible, the process of porting the Arduino libraries and environment from one chip to another. This is, at a high level, possible because anything a computer with a turing-complete instruction set can do, any other computer with a turing-complete instruction set can also do. The hang-up would be on limitations of real hardware (there’s a lot of cool stuff in there, but no infinite data/instruction tape).