There is no federal age of consent law. It varies from state to state. Some as low as 12, other at 18. Some even have a seperate clause that if one party has reached the age of consent, the other can not exceed that persons age by more than X years.
And the age of consent should NEVER become a federal issue.
see Age of Consent
but regardless...my point is that the age can be lowered. And if it can...it will. Which brings us back to kiddie porn. What is illegal today will be legal tomorrow.