Looks like the first ever flashcart to play 3DS roms is coming out. From the video it looks like they're using a different micro sd card for every game, but I'm not sure if it'll be like that in the final product or if this was just their demonstration/proof of concept. Either way, it's interesting news.
http://www.gateway-3ds.com/products.html
http://www.gateway-3ds.com/products.html