Not to mention it'd be cheaper and more enviromentally friendly.
Best way to put it. If it has a 2GB filesize limit, doesn't that already mean you could download an entire NDS image? Most games are between 8MB and 256MB, so if they got their source code compiled and optimized for the 3DS, they could re-release NDS games on the 3DS. The cost would also be cheaper because they don't have to make a chip for the game, they don't have to print manuals (That can be put in an instructions file accessible from the main menu), they don't have to produce card cases and boxes, and they don't have to ship them. It'd be a good idea.