Pretty weak position for the FBI here
The only thing they have going for them is "we know Apple can help us out here on this iOS 7 device, because they have previously", since Apple made big changes in how they manage their encryption with iOS 8 that made their past cooperation with court orders no longer possible.
So this low level meth dealer has pled guilty, and the FBI wants to go on a fishing expedition hoping to find information about other dealers or customers on his phone, and is using that fishing expedition to try to set a precedent for the All Writs Act hoping to leverage that into eventually forcing Apple to hack their own devices like they wanted in the previous case.
This just fuels the fire even more for Apple to 1) make it so they can't hack their own phones even with a court order by shutting down DFU updates and 2) make it so every bit of iCloud data is encrypted with a user controlled key so they cannot turn anything over there even with a court order. I say good on them, the FBI can go fuck themselves.
The outcome of this case doesn't matter, Apple and the FBI will fight it to the Supreme Court, but the time a decision is reached Apple will have made it so they cannot access any data whether they want to or not. The FBI will go whining to congress, and congress will have to see what public opinion is about making a law that forces Apple to create a hole in the protection they have set up, so that the FBI can catch minor street dealers. While they're at it, they should make it illegal for old school dealers and numbers runners who carry a black book with customer information to use codes, because those codes are like encryption in that they force the poor slobs sitting on their fat asses at the FBI to actually do real police work for a change!
Given the public opinion was roughly divided in a case about terrorism I can't see the public supporting such a law, and every tech company will be against it, and business leaders and Wall Street will fret about what it would do to our tech economy. A few people in the pockets of the FBI/CIA/NSA like Feinstein and Burr might support it, but the rank and file never will.