In a 2006 report, Lux Research predicted a $2.6 trillion volume for nanotech including products and services by 2014. For 2005 the share was only $30 billion in manufactured material.
We knew from the NNI's reports that US is now tied with Japan in nanotech funding -both leveled at $2 billion in 2007- but the market size to become 80-100 times more than what's now is a little uncertain.
The problem with nano is first the chemistry. A 3% success rate in an organic synthesis probably applies to nano since their methodology of development is awfully similar.
Then comes the problem of environmental impact. Toxicology studies may one day require prescriptions for nano materials.
Even when all the problems are solved, you may have the problem of public interest and adaptation. People will not drink colored water, won't wear itchy clothes even though they know it will be healthier. You've got to make it acceptable.
Under all these circumstances I see the $2.6 trillion prediction being a little too optimistic. Yes we may catch it or ever surpass it but I would say it's not a smooth sail all the way. Let's not fool ourselves.