Microsoft has revealed that the Xbox Series X will support "expansion cards" that allow for faster storage. Seagate has introduced a Storage Expansion Card for the Series X that will deliver an additional 1TB of game space while maintaining the same performance as the console's built-in SSD.
The company hasn't provided pricing or a release date, but we'd expect the Storage Expansion Card to be expensive when it ships. PCIe SSDs in this class are expensive as a general rule, and making one that’s easily removable won't keep the price down.
Conventional external drives will be fine for unoptimized Xbox One games as well as your Xbox 360 and original Xbox collections, but you'll be running into technical limits beyond that. Looks like next gen means proprietary. Thoughts ?