An unconfirmed response from a Nintendo of America rep via BaxyZ strongly suggests Golden Sun 3DS as the platform of choice:  
 

This better not be true and/or not exclusive to the 3DS.

i really hope not .

Launch title.

Aww shit, I could totally see this being a 3DS launch title. 
 
However, that screenshot is probably fake, because the title of the game is definitely not Golden Sun 3.

I mentioned this during the week ( What launch games do you want to see for the 3DS? ): 
 Now we are looking at a new DS, we will be turning our minds to what might be on the launch table.  There are already rumours that Golden Sun 3 will no longer come to the DS, but rather be a 3DS title (   Go to Source  ).   
 
I can see this happening as Nintendo will want some strong titles for the 3DS launch, and for traditional gamers, that don't come a lot stronger than Golden Sun.  I think in the end, if they switched the development to the 3DS and perhaps we see it in motion at E3, I could be very happy.  Maybe like Gamecube/Wii Zelda, they will launch it on both systems.

It will certainly piss me off, I've been fucking waiting for years for a reason to own my DS it never gets playtime and I can theoretically pirate the games since I own an cyclosDS *mostly used for the cheating function its about the same price as a action replay but has more codes* even though I could pirate there hasn't been many games worth my time so my ds just sits there, Golden sun would make me buy a game and actually play.
I loath all faux 3d so I likely won't pick up 3DS
Edit: cheat functions as in I rent a ds game or buy one then download the rom and cheat on that. Action replay sucks I refuse to purchase datel products anymore and the user made codes are often more and superior.

" @oldschool:  I doubt there's much they would have to do apart from bump up the quality of graphics and sound, after all, the 3D effects that the 3DS supposedly uses isn't software run, it done via the screen itself by how it's able to display regular 2D imagery. Of course, there are ways to accentuate the 2D effect by composing the 2D graphics in a certain way, so I think that's what they'd be doing if it is true.  I hope so as much as you, a good RPG, a solid platformer, and a racing game (Mario Kart) would do wonders for it's launch. "

Since the 3DS is backwards compatible it can still go either way. But I'm willing to trust Nintendo on this one since the DS has given me so much fun.
 
Well, unless it looks like the DS phat anyways.

They didn't appear to be terribly far along as it is. Let's make a reasonable assumption for a change and assume they found out the 3DS would be released by the time they projected to complete their DS game and reacted accordingly.

I hope Not I wont GS now. But it could be cool to watch 3D summons.

A 3DS compatible thing would not surprise me.

 I loved the GBA game!. I hope this is true.

" @animateria said:

" Since the 3DS is backwards compatible it can still go either way. But I'm willing to trust Nintendo on this one since the DS has given me so much fun.  Well, unless it looks like the DS phat anyways. "

 Yea. I doubt they would make this a 3DS exclusive even if they could anyway, there's way too much money in this franchise to be launching it on a new handheld exclusively. It will likely run on both, adding new features for those running the game on 3DS. "

Wasn't that essentially what Nintendo was saying about the Mother series for a long time? 'No information at the moment, but keep your eyes peeled'. Nothing happened though.