Western Digital hasn't shared read or write speeds, probably because they're not going to be amazing on such a high capacity card, especially when it's in the prototype stage. Pricing is likely to be pretty high, though, given that the 512GB option will set you back more than $300/£300. However, videographers may be willing to swallow that cost because they, as the company says, don't want "the interruption of changing cards." Or, you know, you could just buy one to back up every device you own.
Sixteen years ago, SanDisk unveiled its first 64 megabyte SD card. Soon we'll be able to store 1 terabyte. The card itself is pretty small, but somehow memory card makers are managing to cram even more storage into the familiar form factor.