Lots of people own the new iPad. To them, why would they buy another iPad mini? All the difference would be Lightning and the smaller size. Except for rich geeks, people who have the new iPad generally won't buy the iPad mini, especially if they just brought an iPad.
But if the iPad Mini has A6, then it'll be way faster. There would actually be a reason. The difference in cost between A5X and A6 is about $5. In fact, if they put it in the iPad Mini then they might actually save costs - the more you manufacture, the cheaper it goes. We have AppleTV, iPod Touch, iPad 2 and essentially the new iPad (cpu is unchanged for A5X) using the A5 SoC. We only have the iPhone 5 using A6. The price of A5 has probably already been pushed down to the bottom, but putting A6 in the iPad mini will increase sales and decrease the cost of both the iPhone and the iPad mini.
But if the iPad Mini has A6, then it'll be way faster. There would actually be a reason. The difference in cost between A5X and A6 is about $5. In fact, if they put it in the iPad Mini then they might actually save costs - the more you manufacture, the cheaper it goes. We have AppleTV, iPod Touch, iPad 2 and essentially the new iPad (cpu is unchanged for A5X) using the A5 SoC. We only have the iPhone 5 using A6. The price of A5 has probably already been pushed down to the bottom, but putting A6 in the iPad mini will increase sales and decrease the cost of both the iPhone and the iPad mini.