SanDisk ships world's first X4-based flash memory cards, humans wait for capacity inc

http://www.blogcdn.com/www.engadget....ocess-tech.jpg

SanDisk was busy trumpeting the benefits of X4 technology way back in February, and now the company's tooting its own horn once more by shipping the planet's first memory cards based on the new tech. For those who've forgotten, X4 can hold four bits of data in each memory cell, which is twice as many as the cells in traditional MLC NAND memory chips. In theory, this stuff will allow for bigger capacities in the flash memory that we so dearly love, but for whatever reason (read: cost concerns), the first X4-based SDHC and Memory Stick PRO cards top out at just 16GB. Wake us up when we can slam a sub-$50 256GB SDHC card into our D90, okay

http://www.engadget.com/2009/10/14/s...-cards-humans/

I heard of SDXC cards but never heard of X4, does this mean they can double that theoretical 2tb limit on SDXC or is X4 included in that?