Heres why:
Apple needs to differentiate their iPad product lines between the regular iPad and mini. The next version of the mini will get a retina, A6X chip and 1GB RAM...The next iPad will get a new look, A7X and 2GB RAM...
So lets imagine for a moment they update the mini to retina in the spring. What processor would it get, A5X, A6X? They can't have the A6X and 1GB RAM in both iPads, specs are too close. So they would have to update the specs for the iPad 5...thing is, the A7X will not be ready by spring.
Most likely since the mini is selling so well, why update so soon? We won't see any iPad updates in spring...and in the fall 2013
iPad mini, retina, 1GB RAM, A6X
iPad 5, retina, 2GB RAM, A7X
Apple needs to differentiate their iPad product lines between the regular iPad and mini. The next version of the mini will get a retina, A6X chip and 1GB RAM...The next iPad will get a new look, A7X and 2GB RAM...
So lets imagine for a moment they update the mini to retina in the spring. What processor would it get, A5X, A6X? They can't have the A6X and 1GB RAM in both iPads, specs are too close. So they would have to update the specs for the iPad 5...thing is, the A7X will not be ready by spring.
Most likely since the mini is selling so well, why update so soon? We won't see any iPad updates in spring...and in the fall 2013
iPad mini, retina, 1GB RAM, A6X
iPad 5, retina, 2GB RAM, A7X