The MacMini comes very close to fitting the bill but falls short in the graphics department. It already offers replaceable RAM and hard drive. Whats missing is a decent graphics card (ideally user upgradable). Fix this and the MacMini instantly becomes a viable desktop option for the vast majority of consumers, and many professionals, giving Apple a much larger slice of the PC market. With that said, if Apple was interested in producing such a model and/or seriously going after the consumer PC desktop market, they would have done so by now, and I doubt very much if they ever will.
As for the new iPad (5th generation), 25% lighter and thinner sounds good to me providing it does not sacrifice battery life or useability. I trust Apple will make sure the new thinner bezel design works as well or better than the thicker iPad2-4 design. Depending how that goes, I'll be upgrading our iPad 2's for either the iPad 4 or 5. Also looking forward to new features and functionality in an improved iOS!