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.
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.