I presume you know this, because you would have to in order to say something like we haven't reached our "saturation point", yet.
You would need to have a number in mind in order to make statements like that. So, what is it 1 billion, 2 billion, more?
How's this?
FAIR believes we should strive for a system in which continuing immigration does not add to our population size. That would mean admitting between 200,000 and 300,000 immigrants a year.
One night on a cable news program, I watched Dan Stein of FAIR out debate a guy from the Cato institute over immigration and how it has effected the quality of life. I'll stick with FAIR's numbers.