1. If they put a retina display in it, their only screen resolution choice is the resolution of the iPad 4. If they do that the iPad mini's will have a higher ppi than the iPad 4 making it even better than bigger iPad. That is never happening. Apple will never compromise their high end product like that or people who buy the more premium product will start complaining that their display is inferior. The only way the iPad mini gets a retina screen is if the bigger iPad doubles its pixels from its current level and that ain't happening for a few years for technical and economic reasons.
Wrong. The mini has to have a higher PPI anyway because you hold it closer to your face then the full size iPad so you have a greater chance of seeing the pixels.
And because of that its not compromising the higher end version. And they are not going to double the full size iPads resolution again anytime soon. That would make it 4096x3072.
Nexus 10 just came out with 2560 x 1600 pixels at 300 ppi.
No reason to believe iPad 5 won't match that, thereby enabling the Mini 2 to get retina.
Apple will not match that resolution. Will never happen. Everything in iOS is based on 3 resolutions. 320x480, 320x568 and 1024x768, for retina its just a double of any one of those resolutions. For Apple to match that resolution they would have to change the way iOS works and would just piss developers off.