SD cards are everywhere now, and you can get them on the cheap. But SanDisk is not interesting "on the cheap" with the announcement of some crazy, insanely high-capacity flash memory that is more expensive than the camera you put it in.
The new SanDisk 512GB Class 10 ExtremePRO SDXC card retails for $800 and holds a veritable buttload of data. Like, you can shoot your whole day in burst mode. It's touted (by SanDisk) as the highest-capacity card in the world.
All jokes aside, SanDisk mainly has 4K video in mind with these new cards. Ultra high resolution 4K files tend to be huge, and video shooters need a lottttt of card space to store them. It is interesting to note, however, that most cameras that shoot 4K and record to SD cards use highly compressed files, which aren't huge in size, and probably don't require amounts of space that are quite this extreme. The new cards have a read speed of 95 MB/s, and a write speed of 90 MB/s. That should be enough for most 4K video sources.
512 GB is surely enough to get you through the day, but I'm not sure videographers or photographers are going to want to put such a huge amount of data on one single card. If it fails, you risk losing a whole mess of material. Whereas if you use a bunch of smaller cards, you only risk what is recorded to any single one.
You can get also SanDisk's new cards in a slightly more moderate 256 GB version for $400, or 128 GB for $200. [Canonrumors]