It looks like we’ll soon get significantly faster SD cards. Apparently, SD Specification Version 4.00 is expected to be ready by spring next year, meaning the maximum data transfer rate (read/write) will jump from 104 MByte/s to 300 MByte/s. But not too surprisingly, you’ll need to update your hardware to make use of the higher speed.
The data transfer scheme will be changed from parallel to serial, using low-voltage differential signaling (LVDS), which is the case in many other serial connections. The number of pins used in both the cards themselves and card readers will have to be higher than the current nine pins in order to make the increase in speed possible.
The new cards will be compatible to existing hardware, but the maximum speed you’ll get will be just 104 MByte/s. More details can be found in the table above.