Sony is testing a PlayStation 4 console with a 1 TB hard drive, according to recent filings with the Federal Communications Commission.
The new console with the 1 TB hard drive is listed as model CUH-1215B in the FCC documents, as you can see in the image below.
Another "production prototype" console, CUH-1215A, includes a 500 GB hard drive, which has been the only size available since the PS4's release in November 2013.
Though the PS4 ships with a 2.5-inch hard drive, the console's design makes it easy to replace. Sony even provides directions in a PlayStation Knowledge Center article.
Hard drive size is particularly important this console generation because of digital distribution's ascendency and games' demand for more space. PlayStation Plus subscribers, for example, get downloadable games every month. Sony alluded to that segment's profitability in a recent financial disclosure, citing a "significant increase in network services revenue" as part of the Game & Network Services division's success.
Sony's most direct competitor, Microsoft, also bundles a 500 GB hard drive with the standard Xbox One system. However, special edition consoles like one for Call of Duty: Advanced Warfare, include a 1 TB hard drive.