Everyone seems to be complaining "Oh, now I'm gonna have to buy the next iteration that incorporates this frankenstein monster into a sleek form factor." As a launch-day 3DS owner, I can definitely sympathesize with this sentiment.
But I think I question no one is really asking is not "if they're going to do it," but instead "how in the world are they going to do it?"
Seriously. The 2nd circle pad, that's easy. It'll probably go right under the face buttons. But I'm looking at my 3DS right now, and wondering where in the world would they fit those extra shoulder buttons? Right under the current ones? You can't fit it there, or you would be accidentally hitting both L1/R1 and L2/R2 together all the time. That space is really tight because of the hinge. Are Nintendo going to have a bit of plastic protrude, like little devil horns, in order to fit the extra buttons? That'd be crazy. Will they completely abandon the current clamshell formfactor all-together, or make it thicker just to accomodate the added triggers?