Not much room to grow? Says who? Did I miss the referendum in which the computer science salary cap was enacted into law?
The fact that companies are not charitable institutions is exactly the point. If they want more or better engineers they are welcome to pay salaries that will motivate such people to work for them, much as the petroleum industry is currently doing.
Then let them carry on. Most of these companies are global in nature already. My naive view of the plea for more foreign tech workers to enter the US is that the majority of those controlling the money just really really really like like in SF and don't want to leave. When there's talk of tech worker shortage, there's not even any really serious effort to look around the US. Nope, the hive mind is in SF, and they'll move heaven and earth before they have to move someplace else.
The fact that companies are not charitable institutions is exactly the point. If they want more or better engineers they are welcome to pay salaries that will motivate such people to work for them, much as the petroleum industry is currently doing.