Second generation of iPad Mini or iPad Mini 2 is claimed to be on prototype stage right now. It’s said that iPad Mini 2 is still on development stage because Apple still has a problem with iPad Mini 2 battery.
Most likely it’s about the battery life time. Retina display on iPad Mini requires much energy from the battery, but with small body, the tablet can’t pack a battery with big dimensions.
Citigroup predicts that iPad Mini 2 will be released after iPhone 5S and cheap iPhone released or between late September to October this year.