3D printing is nice for prototyping and for custom fitted, user-adapted items. This will likely remain a high-end segment for a long time. Eventually, we might be going for an economy in which every product ordered is printed and produced adapted on demand to customer's wishes, but I'm not sure how realistic that is. There will likely always be something to win by exploiting scale. Especially for low-end products.
2D printing didn't replace print shops with specialized mass-production equipment for printing books/magazines either.
Really I don't think it will change even the prototype industry much, maybe for first runs but for production models I like to select the finish, shine, paint, etc and a 3D printer just can't do that at the same cost. Even comparing turnaround time, I can get a prototype rushed from order to me in 24 hours for less than a $1000. If you're willing to wait a week, a few hundred and it looks like a factory part.
My prediction is that in order for these machines to become mainstream some companies will need to allow reproduction of their product designs first, and create a digital channel specifically for delivering the designs to consumers and their 3d printers.
As that will clearly decrease the need for manufacturing in China, the ability for us to print the goods they are now creating cheaply will hardly affect their economy.
For now, unless you have a Makerbot and want ABS lego, consumers simply can't afford 3D printing their toys with commercial 3D printers. It's just like with regular printers: the ink is more expensive than the printer itself!
However, that's not to say that it will always remain that way and I can't wait for that day to come!
Try printing a full-length book on your desktop printer, and let me know how much the total cost of your time, the paper, and the ink is.
Compare it to the cost of a normal paperback and then note that the quality of the typesetting on your printed version sucks, and there's no cover.