[tadah]

That would be the way to go, but why invest in x86 at the time where it mattered the least to Apple's bottom line?

ARM is the way to go.

[tfha]

Is there a reason RISC V is off the table?

[mrweasel]

As for right now, speed and features. Apple is already pretty invested in ARM and have the in-house experts. Managing and developing two processor architectures in parallel is a massive duplication of effort, just to avoid paying ARM a licens, a licens that Apple can easily afford.

In the long run, no there's no reason why Apple couldn't use RISC V in place of ARM, but not without a large upfront cost.