The SD Association has released SD Express specification, which they call “a Revolutionary Innovation for SD Memory Cards” From the press release: “The PCle interface delivering a 985 megabytes per second (MB/s) maximum data transfer rate” and “the maximum storage capacity in SD memory cards grows from 2TB with SDXC, to 128TB with the new SD Ultra Capacity (SDUC) card.”
You can download the release here
Read more on the SD Association website