When will 3D printing become mainstream?

I guess a lot of enthusiasts are asking themselves, when 3D printing will become more conventional. 3D printing has been getting more and more attention in the past year - articles in newspapers and reports on TV are spreading.

I just read a post on fabballoo.com which dealt with the timeframe when 3D printing picks up among a wider audience. According to Olaf Diegel, Director of the Creative Industries Research Institute at the Auckland University of Technology in New Zealand, 3D printing will be common in households in no more than 2 to 3 years:

" I would predict within the next two to three years, everyone that has an interest in design will have one of these at home, and it's only a matter of two or three years before they become mainstream."

I had a course at the University of Wisconsin past semester and a professor of mine, Aric Rindfleisch had similar expectations.

So what has to happen?

1. Probably most important: Printers have to either increase in quality (printers like makerbot or ultimaker) or more expensive printers (like from dimension) have to decrease in price. 
2. We definitely need some sort of more professional infrastructure where people can buy materials or co create designs. I know thingiverse is trying to do this...but I'm must say I am not a reaaal fan
3. CAD file conversion difficulties: STL is what is being used by makerbot and most other low cost 3D printers. This may work for prototyping...but I want more ;) Manufacturers will have to bring out printers that can work with other, more sophisticated formats. Consequently we need printers that can do more than print stuff in plastic

My thoughts on the timeframe - a lot of stuff happened in the last 2 years. But I doubt people like my mom and dad will buy a makerbot or a different low cost printer just cause they can print small objects in plastic...with to be honest, lacking quality. SLA is better in quality, but material costs are $$$. So I guess...2,3 years may not be realistic. More like 5 to 7 till it really kicks off. But I would be happy to be proven wrong.

What do you guys (and girls) think?