As most are aware of, the M3 team released an SD adapter for the Nintendo Developer's System/Dual Screen. This device allowed owners to play .nds and .gba files off of their memory stick and was the must-have cartridge for the NDS. The current version of this device sticks out about 1cm from the NDS and even more from the NDS Lite, which makes it less portable.
Recently, the M3 team announced to other news sources (not us ) that there is a new version in the making, M3 SD X. This version will be much smaller and is slightly larger than a normal GBA Cart. \
According to GBA Alpha, the cart would be released on the 24th of this month I think.
Here's all of the pictues I gathered:
Comparing M3 SD to newer version: