According to a recent report, adding a Retina Display to the iPad mini could add 30% to Apple's total parts cost. Like the original iPad, however, I think the Mini is two years away from Retina. Also, (like I said about the iPad with Retina), I don't really care unless the weight is the same or lighter than the current model AND the thickness remains the same or thinner. It is all about size, not the display... that is, even if they did bring it to market this year.
Now that I have switched to a Mini, do I miss a sexy Retina display on an iPad? Yes, but not nearly as much as you would think. The iPad Mini's display is just fine in comparison, for now - although I do think Apple can bring in a better display (one akin to the Nexus 7). I also believe the big mods this year will be a faster processor, hard drive space (@128GB), and (hopefully) more RAM. These are all specs I would gladly upgrade to, but I won't.
In my opinion, the Mini IS the iPad to get - even right now, without the Retina. Give me a Retina, but refuse to compromise on size and weight, as the size and weight is the Mini's biggest advantage.