http://en.wikipedia.org/wiki/Helium#Modern_extraction_and_di...
"According to helium conservationists like Robert Coleman Richardson, the free market price of helium has contributed to "wasteful" usage (e.g. for helium balloons). Prices in the 2000s have been lowered by U.S. Congress' decision to sell off the country's large helium stockpile by 2015."
I'm a bit skeptical of the quoted numbers, but even if they're a magnitude off there's still plenty left to be extracted. The US alone apparently still has enough proven helium in natural gas reserves for the next 40 years of worldwide consumption, and estimated unproven reserves for the next 40.000 years:
"Diffusion of crude natural gas through special semipermeable membranes and other barriers is another method to recover and purify helium.[84] In 1996, the U.S. had proven helium reserves, in such gas well complexes, of about 147 billion standard cubic feet (4.2 billion SCM).[85] At rates of use at that time (72 million SCM per year in the U.S.; see pie chart below) this is enough helium for about 58 years of U.S. use, and less than this (perhaps 80% of the time) at world use rates, although factors in saving and processing impact effective reserve numbers. It is estimated that the resource base for yet-unproven helium in natural gas in the U.S. is 31–53 trillion SCM, about 1000 times the proven reserves."