They will always be cheaper than US labor. And there are other advantages like employer loyalty because they cannot easily change job, which means employers can push them very hard and they won't quit - because its complicated to shift to another employer and they have to restart their green card.
I think behind all this is the feeling that the best opportunities are given to foreigners who then rise up the ranks, opportunities which could have been given to Americans.
Regarding immigration in general, the left continuously argues to keep low-paid foreign workers here to the benefit of large corporates. The justifications of "all of Silicon Valley companies support foreign immigration" makes perfect sense for these companies, but not for the nation. Silicon Valley is a bubble.