Edward Hasbrouck has pointed out that under final Real-ID rules, you won't be required to show ID to fly. He also carefully differentiates between Real-ID and Secure Flight. This is an important article for anyone interested in this issue:
There's been a lot of confusion in the last few weeks as to (1) whether the USA
Federal "Real-ID Act" will change the requirements for personal identification
documents for airline passengers in the USA, and (2) if and when the Real-ID Act
is fully implemented, will it be impossible to fly without showing a
government-issued "Real-ID" document?
Now that the final rules for implementation of the Real-ID Act have been published, those questions can be answered simply and definitively: No, and no.
No publicly-disclosed USA Federal law or regulation currently requires domestic USA airline passengers to present any sort of evidence of their identity. If you have a valid ticket and comply with their general rules, airlines are required by Federal law to transport you, regardless of whether you have any identification papers (government-issued, "Real-ID" compliant, or otherwise). The Real-ID Act and its rules will not change any of this. You will still have a right to fly without ID, even under the Real-ID rules newly announced by the USA Department of Homeland Security (DHS).
There are other pending rules which, if they are allowed to go into effect, will require both government-issued papers and permission for international travel to and from the USA, beginning this month. And the proposed Secure Flight scheme
would extend those papers-and-permission requirements to domestic air travel
within the USA. Those are significant, and call for immediate litigation and
ongoing refusal to comply with illegal orders. But those are all separate from
the Real-ID Act.
Much of the confusion about the Real-ID Act and air travel
has come from misunderstandings of the current rules, and from imprecise
reporting about the proposed Real-ID Act regulations.