Despite assurances that it was only asking Apple to help unlock and extract data from one phone, the FBI reportedly has 12 more devices waiting to be unlocked. As with its current case against Apple, the FBI is apparently seeking court orders citing the 227-year-old All Writs Act in order to compel Apple's help. However, unlike the San Bernardino case, the Buraeu is evidently not linking these devices to terrorism investigations.
From The Wall Street Journal:
The dozen other phones now the subject of legal battles were seized in a variety of criminal investigations, but they are not terrorism cases like the San Bernardino investigation, people familiar with the matter said. The dozen or so cases are also distinct from San Bernardino in that many of them involve phones using an older Apple operating system, which has fewer security barriers to surmount, these people said.
The case in San Bernardino involves Apple being asked to help extract data from an iPhone 5c used by one of the San Bernardino shooting suspects. In order to do so, Apple would need to write a special version of iOS that bypasses certain security measures in the phone's operating system. While the FBI has insisted that this tool would only be used in this case, Apple has argued that this case would set a precedent that could lead to less secure devices for all Americans.