Would be fascinating to see how many people from TCS, Wipro and Infosys ended up moving to Apple, Amazon, Facebook, Google and Microsoft after a few years in the US.
Some of the larger product companies employ contractors from those firms. I know quite a few people employed by TCS who work at Apple, and some of them plan to stay with TCS for 10 years or more. Those big companies are still taking advantage of these cheap visas even if they're not employing the people directly, and that definitely impacts wages in our field.