In an announcement earlier today, Sony confirmed that the PS4's upcoming 4.50 update will give players the ability to add their own custom wallpapers on the startup screen and, more pointedly, allow for external HDD support. The report states that any external drive with USB 3.0 will work and the system is currently beta-testing the update at the moment. Sony also confirmed that the update will allow up to 8TB HDDs on the system, which should keep players going for years.
No specific date has been set for the 4.50 update, but it's likely to be coming in the next few weeks or so. As well as this, the 4.50 update also makes 3D Blu-Rays compatible with PlayStation VR and allows for stereoscopic viewing. Because, let's face it, our 3D Blu-Rays were just gathering dust beforehand.