You do know that they have already released a newer version of this phone? Presumably this new version is already not susceptible to the method being used by the FBI.
Do you think Apple is going to attempt to R&D a patch for all their earlier 5C Iphones? (Assuming it can even be done.)
What I’m trying to explain is that Apple can review testimony by any expert witness summoned in this case to figure out how the FBI was able to access this phone and plug the hole. The technology may have moved on and later models may not be susceptible to this exploit, but I would imagine that they’ll still want to fix it.