Yes, but that's a big "if". When you start looking at it from the perspective "I don't need binary compatibility with microcontrollers", you realize that opcode

Yes, but that's a big "if". When you start looking at it from the perspective "I don't need binary compatibility with microcontrollers", you realize that opcode space has been wasted on things that you don't need. It's similar to how x86 has wasted several single-byte encodings on instructions that are never used in modern programs. The extensions that you end up wanting to do overlap with the base ISA, but with slightly different semantics. It's manageable and you can live with it, but already from the start you have an unnecessary legacy that needs to be handled. If there is enough consensus in the industry, a new revision may be the best way forward.