Eurogamer, Fracture assistant producer Jeffrey Gullett said it's something they've looked into it but that there's an issue of size limitations for a DS version.
Said Gullet, "The cart size of the DS makes it impossible to put out ports of any of our old graphic adventures ... There's literally not enough room on those carts to put the games out." The standard DS cart supports up to 256MB (but with slower data transfer speeds), while the DS version of ScummVM is just over 7MB. We're not sure if Gullet meant the entire LucasArts adventure library wouldn't fit on a cart, but we're willing to bet you could at least get the first three Monkey Islands under 128MB.