[hopespringseternal]

Certainly, we should be aiming for at least replacement levels. If our native birth rate is lower than replacement level, we can make up the difference with sensible immigration policies.

Two things that will never happen:
1) Birth rates will not be at replacement levels.
2) Our politics will never allow sensible or even sane immigration policies.

[Modernman]

1) Birth rates will not be at replacement levels.

We're almost there now. The US rate is 2.08 children per woman, while the theoretical replacement rate is 2.1.

2) Our politics will never allow sensible or even sane immigration policies.

Maybe not in the current political culture. I think this is a case of "it's going to have to get worse before it gets better."