I don't think they're going to do a redesign for a while. They're barely making money off the current ones to be designing and making a new one.
I think now would be the perfect time for a "relaunch" of the 3DS. There's a great library of games now, they're adding support for a 2nd analog stick, the Vita has launched and Apple's new iPhone and iPod Touch are nearing. They can rename it so there's less emphasis on the 3D (but still have it as a selling point) and nullify any perception issues of it just being another DS with 3D.
It could be sold alongside the 3DS and at a premium price (closer to the iPod Touch/Vita price)