The act has never been used (as far as anyone can tell) to force Apple or anyone else to write new software. Considering the provenance of the Writs Act, it's unlikely that the Framers of the Constitution ever considered that possibility.
It's no surprise that Apple is gathering some powerful allies in its upcoming battle with the government. The Software and Information Industry Association has announced that it's in Apple's corner in this issue.
"Our industry is committed to working with law enforcement to keep Americans safe, but we strongly believe that the government's position in the Apple case will do more harm than good," SIIA's senior vice president of public policy Mark MacCarthy said in a statement issued by the association.
"This case is not about one company or one device. It will ultimately affect the trustworthiness of every device where data is secured. The government wants to force companies' engineering staff to create malware that weakens security on a mobile phone’s operating system," MacCarthy's statement said.
The Electronic Frontier Foundation sided with Apple saying that it expects the government to use such a capability frequently. "The U.S. government wants us to trust that it won't misuse this power. But we can all imagine the myriad ways this new authority could be abused," the EFF said in its statement.
But protesting the court order can do only so much. Ultimately, Apple is still under a court order to produce a means for the FBI to gain access to Farook's iPhone. Presumably, the company will appeal the order, going all the way to the Supreme Court if necessary. Unfortunately, this is a risky strategy because the high court can decide that the government is right and that Apple must comply.
The risk goes beyond Apple being forced to do the FBI's bidding. It will also create a precedent that allows such demands in the future, at which point such refusals would fall on deaf ears. Because this case is unprecedented, there's little reason to assume that the Supreme Court would see things Apple's way.
But maybe there's another approach that would solve the government's problem, while still keeping a "master key" out of the hands of the government. Suppose Apple were to create software that would remove the 10-tries limit, but not share the software with the government. Apple could simply modify the iPhone software and give the phone back to the government.
Then the FBI investigators could run a brute force procedure for as long as they needed to find the right access code to break into Farook's phone. While it might not satisfy the government's desire for instant gratification, it would eventually provide the access they are demanding.
Because the iOS 8 lock codes are only four numbers long, giving a total of 10,000 possible combinations, it may take a while, but it won't take forever. While this would deny the government the master key it wants, all it's really asking for is access, and it would get that.