The sealed box makes sense for the average iMac buyer.
The thread OP here is not an average iMac buyer. Neither am I. I'm very happy with my 2011 model, except for the DVD drive which, like every DVD drive I've ever owned, has failed. Unlike an external, it isn't worth the hassle to replace it, so I'll just go ahead and use an external like I do for my laptop the four or five times a year I need it.
Anyway, there are two things that you don't like about the new iMac: lack of a DVD drive, and lack of upgradability. But, neither of those matter to most people.
There is one other thing that you, a power user, shouldn't like about the new iMac: it's basically a laptop. Miniaturized components, all sealed in place. The type of user who wants to be able to upgrade things shouldn't really want that: you want a Mac Pro.
The new Mac Pro isn't too much farther out now. Well, it may be a while. But, it's going to happen in 2013. I don't think that MR knows anything about it, except that it's probably going to be built in a new facility in America and probably with a lot of automation; the way Macs used to be built when they used to be made in America. Which might drive down the cost a bit- although they never were cheap back then. Hah, I have no basis at all for speculating that the Mac Pro will be available and affordable. But I know it will be a more suitable computer for your desires than the iMac.
So, hold out for the Pro.
TLDR:
1) Most people don't want an upgradable computer, so it makes sense for Apple not to make its main line upgradable.
2) Most people don't want a DVD drive and Apple doesn't want to keep fixing them, so it makes sense not to include them in the main lines.
3) You should wait for a Mac Pro.
