I'm not sure why people are so confident that there will be a retina version next year.
If they went with the bare minimum res to achieve 'retina spec' on this size of screen, it would be something in between 1024 and 2048, resulting in nasty scaling for unoptimised apps, and a third resolution for iPad app developers to worry about.
If they made it full-on 2048 to match the full-size iPad, it would look better than the full-size iPad. Unless they increase the full-size iPad res again... which seems equally as unlikely for the same reasons - scaling, development troubles. They would need to do something special to the full-sized iPad to keep it appealing otherwise everyone will pick the Mini next year.
Even if the big iPad was faster, I don't think Apple would allow the Mini to have the better screen.