I just bought a second iPad Mini last week, so I don't agree entirely. We have 7" Samsung tablets, and they're annoying to scroll around websites with. They are much better at movies and Angry Pigs IMO. A retina Mini would be nice, but I like the current Mini's screen size, light weight, and build quality. We have iPad 4's as well, but they're a bulky and heavy compared to the Mini for carrying around.
I would agree that minus a retina display, buying the next incarnation of the Mini might not be worth it for me. Our Mini's are still functioning perfectly, and unless they reduced the weight by 50%, or did something else dramatic, there's not much else to improve on.