I have to say, whoever at the FBI decided this was the right case to push their new doctrine, could have done his/her homework a bit better. Technically speaking, this is the last iPhone you can actually crack without assistance from Apple. They are making it harder for themselves. They only have to wait for another major incident, retrieve (or plant, why not) an iPhone 6 from the scene, and do it again, this time for real.
Unless they are trying to pre-empt something else (like the recently-touted shift to "devices even we can't access" from Tim Cook, which may or may not be simple advertising), they just picked the wrong time to stir this particular pot.
I suspect the main driver in picking this case had nothing to do with the technical details and everything to do with the emotional aspects. The general public won't follow the technical bits and the emotional appeal of the case (terrorists! scary!) has clearly been a boon.
This case isn't just about Apple though. If the FBI wins this case, it becomes a precedent that can then be turned around and used on ANY hardware or software company in the future.
> this is the last iPhone you can actually crack without assistance from Apple.
That's being pretty liberal with words. It's more difficult to crack more recent versions, but saying it's impossible is putting too much faith in the creators of the device and too little in determined people who would want in.
Unless they are trying to pre-empt something else (like the recently-touted shift to "devices even we can't access" from Tim Cook, which may or may not be simple advertising), they just picked the wrong time to stir this particular pot.