If I were Apple (like they care about my opinion) here's how I'd arrange the new line, to rationalize (ie not scare off buyers with too many choices) and to clean up the cruft of the past.
Each of the iPad and iPad mini lines splits into two:
We have an iPad S which comes with A7X, TouchID and (greater than 70% chance) 2GB of RAM, 802.11ac, and the A7X has three CPU cores.
We ALSO have an iPad C which is basically the guts of the iPad4 wrapped in plastic, and takes the place of the iPad2.
Likewise we have an iPad Mini S which is basically a scaled up iPhone S (apart from the camera) and costs $50 more than the existing iPad.
And we have an iPad Mini C which is basically an iPhone C (stripped down to as cheap as possible) to get to a retina iPad mini at the existing price point.
The moral is that going forward (at least for the immediate future) iOS devices come in "leading edge/expensive/metal" and "fun/less expensive/plastic". We've seen similar eventual unifications of a single design style across Macs after a few years where the different product lines wandered in different directions.
These, I think, are all the "obvious" changes. The great unknown as the "one more thing" is the mythical 13" iPad.
I can see reasons why this makes sense for Apple, even if it's not expected to be a great seller.
(a) It's a halo item. Whatever magical A7X CPUs can be binned at 2GHz (or whatever) rather than the 1.6(?) GHz of the standard iPad get displayed here as a "we're the king and always will be" statement to other vendors.
It likewise allows Apple to test-drive expensive, high performance (and perhaps even hot) chips before they get sent into the mainstream. Eg it could be the first iOS device to ship with 4GB of RAM (take that all you "64-bit is so dumb in 2013ers!") And it definitely gets 802.11ac, even if the iPad S does not.
(b) It comes with new OS features (most obviously two windows visible at once) to shut up the claims of what a wonderful device Surface is for work.
(c) It makes for great ads (eg radiologists examining X-rays, pilots looking at documents, architects looking at drawings --- basically iOS for the rich professional and his deep-pocketed company).
On the negative side, it introduces yet another screen size. Less than ideal. But the old iPhone size is going away soon, as are the non-retina iPad and iPad mini. Essentially dev's will have four all-retina sizes to target (maybe three depending on how retina iPad mini is handled). That's probably not an unbearable burden, especially since for most purposes you can get away with only two real "layouts", phone and tablet, and rely on auto-layout to just let you see more stuff on differently sized tablets.
I'd rate the 13" iPad as 50% likely.
Having 4 new iPads a year (plus the possibility of a 13'') would be the beginning of the downfall of apple. Just no.
