Counting the XL as an iteration is like calling a different size of shoes a different iteration.
The XL is the same device, just for old people with incredibly bad eyesight that don't need to use their portable device as a portable device.
Right now the New 3DS is basically going down the same road as the DSi. So I imagine the next step will be a new DS. They'll also likely call it a New 3DS U, so fans wont get confused and think it's the same thing. Because nintendo naming logic.
Also the "new" 3DS didn't do much. It's a bit better at playing games (and 99% are already optimized to run fine on an original 3DS to begin with), the teeny tiny analogue nub is a joke, and 3D is still useless old 3D.
The cover plates are kinda cool though, I didn't know that was a thing.
But point is, they'll soon need to come up with something new. Better layout, more power, hopefully not a new gimmick.
Damn this post is horribly written. I shouldn't type after frying in the sun all day.