The new specification provides two faster transfer rate options for SD Express memory card, using either PCIe 3.0 x2 or PCIe 4.0 x1 architecture to deliver 2GB/s data transfer rates. Cards which use the new specification will support storage capacities up to SDUC, which means that they could be available in capacities of up to 128TB.
See New SD card standard boasts insane transfer speeds
The SD Association has announced the SD 8.0 specification for SD Express memory cards, which boasts support for significantly improved transfer speeds.