You should have replaced your mini 2 a long time ago. Go for the mini 4 now on sale if you really want a new mini. If you don't, you risk waiting until spring and finding out Apple doesn't announce a new mini or it's not as big of an upgrade over the mini 4 as you thought.
Worst case scenario is that the mini 5 actually is incredible and you sell your mini 4 that you already got on sale so you don't take a massive hit and purchase the new iPad mini, and how bad is that scenario where the new iPad mini is amazing? 😛