Microsoft has confirmed the Xbox Series X will allow for hot swapping the external SSD. This will allow a console peasant to be able to have more games on hand. While extra SSD units are expensive ($220) they will work directly with the Xbox Series X.
Recall that the Xbox Series X uses PCIe 4.0 so there is a NVMe interface for the SSD unit to afford it very high speed of up to 16GB/s maximum.
Microsoft has worked hard to bring a superior gaming experience to the Xbox. The Xbox Series X represents several breakthroughs in console technology.
Microsoft has not given any projections regarding the number of units they are expected to sell this fall. Sony was forced to reduce inventory as production fell short at TSMC.