My guess is they will retain "parts pairing" from a technical perspective, but frame it as an anti theft measure, and focus on preventing use of stolen device parts.

Perhaps they'll relax the restrictions on "non first party" components (likely you'll lose some functionality that aftermarket parts don't actually support), but use pairing to lock out parts from stolen phones.

I suspect that part of their strategy is to try to make stolen iPhones less attractive to thieves, and effective parts pairing would likely reduce the market for stolen phones stripped for parts.

Of course, if you can "blank" off a stolen part to appear as an unofficial one, that doesn't work! That idea is therefore likely to face challenges.

The challenge will be what is really meant by parts pairing - to some extent if you want to do some features securely (say touch ID), you probably want to pair the reader to the secure enclave with a shared AES key and similar. There could be tooling to reset and re-establish that pairing on an unlocked device.

Legislation often struggles to define exactly what is required though, so it will certainly be interesting to see how Apple responds.