I speculate this is somewhat less likely now that the NVidia / ARM deal has fallen through but surely Apple wants the option at least.
Apple probably already use RISC-V designs somewhere in their hardware stack. But the ISA will remain ARM for a long long time.
Even Apple Silicon has a ton of stock ARM cores to control various SoC tasks.
I speculate this is somewhat less likely now that the NVidia / ARM deal has fallen through but surely Apple wants the option at least.