I'm in the same boat.
At the moment I don't see the upgrade as worth it since we don't know if Nintendo will push more exclusive N3DS games. It's not even out in NA/EU yet and might not be for a while so it could be years before they transition to the N3DS or come out with an actual successor to the 3DS.
If you want to guarantee you can play the the possible exclusive N3DS games then get one while you have a guaranteed chance to get a N3DS that works with GW.
If you don't think there will be many exclusive N3DS games and are happy with the current 3DS than don't buy a N3DS.
I am currently in the latter category even though I want a shiny New 3DS, but I realize that the upgrade isn't really worth it to me since I rarely ever use the 3D and don't think Nintendo will put out a ton of exclusive games, the install base of the 3DS is just too high to ignore and third parties probably won't ignore it either.