While the CFExpress 2.0 standard promises speeds reaching 4 GB/s, Sony's first cards will be on par with the average NVMe SSDs. The new CFExpress cards are still meant for professional DSLRs and video cams, however, since they support the new NVMe interface, they can also be used as external SSDs for compute clusters and enterprise servers.
https://www.notebookcheck.net/Sony-presents-CFExpress-memory-cards-that-rival-NVMe-SSDs-for-highest-read-write-speeds.411009.0.html