Recently, immigration to the U.S. is declining and in the near future, anti-resistant bacteria is going to wipe out a significant portion of World’s population. (Just think anti-drug resistant TB)
LEGAL immigration is not declining. We are still taking in 1.2 million a year and that number will go up because of lack of quotas on certain immigration categories like spouses and children. There are over 4 million intending immigrants waiting overseas to enter this country. They are just waiting for their number to come up after completing all the required paperwork.
Illegal immigration is allegedly down due the sagging economy and better immigration enforcement. I don't put too much stock in the government estimates, which are meant to fool the public so they can push for an amnesty.