Just incase, since you don't know, I'll let you know. Korea Nexon, INC themselves attempted this and dropped it cause they couldn't.
Don't even say it'll be out 'soon', it's been at first declared by kMS and dropped, then a homebrew of it was attempted and said to be out in Dec 07, and didn't, they were often mismatched to the point of IGN having it on their list at one point and then taking it off.
Let me rephrase this once more, this will NEVER happen. The closest thing to an MMO on the DS is ndsRO, and as you can see, the graphics are similar to GTA1, the NDS just can't handle the overload of server information back and forth via WiFi AND high-end graphics. If you even had DS, except only seeing their big ass heads as maybe 4 pixels, so that people could fit evenly.
If I wanted to be really serious about it, I'd tell you that generally Maple is 800x600 pixels standard.
The DS screen is 256 x 192 pixels.
Things would be .32 the ratio, or in other words approximately 3 times smaller than normally. Now I'll admit that MS graphics like the heads on characters can be big as hell, some things are already so small that it would be redundant.
There would be so many problems with it it's not funny, yes they could show most of it on one screen, and have all the HUD on the bottom screen, but even that would become problematic.
You can look through Korea Nexon's site, and you'll see that they haven't had information up for along time. In fact, if you know Korean, google it!