The Future of 3D Printing

One of the main question I often discuss with people is about the future of 3D printing and thus, the future of our 3D printing marketplaces like Threeding.com. Basically, there are two main theory among the people in the industry. 
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One of the theory (I call it the optimistic one) is that soon a universal material will be found and 3D printers will become available in almost any home. This will be the 3rd industrial revolution, significant part of the manufacturing will return from China, there won't be transportation costs, etc. I really like this future. Then people will buy 3D printable models for sites like Threeeding.com and I quickly become Mark Zukerberg :).
 
The other theory is the one I call it the pessimistic one. Many people say that the ownership of 3D printers will never be even a quarter from the number of 2D printers owned by consumers. This theory is based on the fact that 3D printers have been around us for 25 years and there is no reason this to change soon. Furthermore, there are 3D printers that work with different materials  and it is economically not justified for consumer to own five different printers. That's 3D printing will develop but but in the form of services.
 
I think both theories are to extreme. Universal material won’t be found soon (if one day found at all) but there are going to be printers that work with several different materials. In the same time, I believe that soon or later one of the tech giant will enter the market and that will decrease the prices of consumer printers significantly. Thus, a lot of people will buy 3D printers and they will use for 3D print relatively simple models (like the Lego for their kids) and they will be buying 3D printable models from Threeding. If people need something more specific they will go to the a services provider near the neighborhood. 
 
This is like 2D printers. A lot of consumers have A4 format printers in their home. Anytime they need wider forma printers or fast speed printers they just jump the closest copy center. 
 
That’s my view. I would be happy to hear your thoughts.