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.
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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.