The SD specification has been expanded to SDXC which allows up to 2 terabytes at a transfer rate of 104Mb/s this year increasing to 300Mb/s at some stage.
See fourthirdsphoto forum for more details.
Having just had a new cheap Photofast SD card suddenly fail without warning, I’m not sure I would like losing 2 terabytes of data in one go.
Nevertheless, it should be welcomed by those with compatible camcorders to give them much longer recording of videos, and maybe for those who like to show their mates their videos from their mobile phones.