The main question I still havent got an answer to is: will the MK4's still need SRAM on a GBA cart to work like the passme2z and passkey mini supposedly do? From the sounds of it they wont.
Just to set others minds at ease a tad: the biggest reason why running stuff directly from the SD on MK2/3 is not full speed is because the drivers to get files from the SD card are not hardware based, they are coded into the menu and patched into the game; they eat a large amount of the speed of the MMC mode SD slot and some of the CPU time of the DS itself.
Remains to be seen (as always) what the software will be like and whether it will need tonnes of time to develop.
No fear though, MK2/3 and XG or Neo carts have not been left behind as outdated and software for them is still being developed (unlike some
other overpriced cart's software I know of)