Supporting 64-bit ARM systems

Perhaps I'm dating myself just a little, but this looks like the 8085->8086 transition. There was no 8080 code out that would run on the 8086. 8086 did retain the weird side effects of 8080 arithmetic and attendant conditionals, so transcoding was easy to automate. 8085+1=8086 was a shuck that worked.

DEC provided a translator from x86 to Alpha, and the translated code ran lots faster on Alpha than the original code did on x86. IIRC, interpreted x86 ran as fast as x86. It didn't save them in the end. How the market will respond to a new architecture depends on details, and nobody knows which details will turn out to be important.

Compatibility can be a trap: IBM OS/2 ran windos programs unchanged. windos could not run OS/2 programs. Which target should you code for?