No way Apple is going to raise the prices of either iPads. History speaking, Apple other retains or drops prices.
The ipad Mini retina isn't going to replace the iPad 2 ( it doesn't make sense) Sizes are different to start with.
What's more possible is that Mini retina, if it does come will slate in $329 (wifi only) and the the Mini will shift to perhaps $279-$299 bracket. Whether they are going to make that the first gen or a newer updated A6 model non-retina Mini is anybody's bet.
There is still the outside chance that Apple may drop the price of the full size and get it to start @ $399 for 16gb, $499 for 32gb, etc. If no, They aren't going to increase the price but retain the $499 for 16gb, and so on. The mini may continue to be sold in configurations maxed to 64gb, but I have my doubts. The mini is essientially the ipad in a smaller size, so apps will have the same size, so you can't really tell people that u can only have that much space because u got a smaller screen.
then comes the possibility of the A6/A6X being updated to fit into the 28nm process or a more refined 32nm process ( similar to what happened to the A5), helping it become a more power efficient model that can perhaps slot into the Mini Retina.
And why would Apple drop the 16gb, and start the ipad @ 32gb from $599, making it ridiculously expensive to buy.