When, not if, will full-body "naked scans" become mandatory in the USA?

Travel blogger Christopher Elliot has an informed post up about the odd timing of the latest terror scare, and a theory that this might be "just another cleverly-timed event that pushes us toward mandatory full-body scans at the airport," just like the underwear failbomber Richard Reid conveniently ended a lively debate about the privacy issues posed by "strip-search machines."

If you aren’t a conspiracy theorist, then last weekend’s foiled bomb plot will just strike you as an interesting coincidence. Which it certainly is.
No matter who you are, though, the happenings of the last two weeks, which include the Transportation Security Administration’s imposition of new enhanced pat-down procedures for passengers who refuse the full-body scans, the terrorism scare, and a pilot who refused to undergo the TSA’s new screening, all lead to the same question: When will the government force us to go through these new machines?
Probably a lot sooner than we think.

When will full-body scans become mandatory?