Why would they go with SD as the media storage? It's only advantage is accessibility. Cost for UHS-II cards is largely equivalent to XQD, and XQD cameras can have the hardware updated to support CF Express (like what Nikon is doing for the D5/500/850 and Z6/7).
100MP, 16-bit RAW files are going to be HUGE in terms of file size. I really don't see why they would go with what is the slowest of the current "high-end" memory storage options (UHS-II SD, XQD, CFast 2.0)