Read it again, I was comparing a (new) retina Mini, not a current gen Mini. And everything faster than an A5 chip (that is in the current Mini) can deal with basically everything you can run on it easily.
You already didn´t gain much from the move from iPad 3 to an iPad 4 (A5X vs. A6X). An A7X is going to be even faster, but applications and iOS are limiting you in such a way that you get almost nothing in return apart from synthetic tests (the ones companies do to make you buy their devices). iOS is just too well optimized for current hardware.
There just are not enough applications that make use of it on the current iOS if you compare that with high-end PCs for example. An A6X is already blazing-fast and if Apple adapts that (or even an A7X-variant) to the new Mini, there won´t be much applications left (web browser, scrolling - although that is also RAM and bandwidth limited) that can show you any difference.