The Treasury recently responded to concerns about the temporary nature of the increase in the basic exclusion amount by publishing proposed regulations. For a full explanation, see the introductory material in that document. Basically they found one situation where a change in the regs is necessary to make it all work so that taxpayers would not be double taxed or otherwise deprived of the benefit of the temporary increase after the amount drops back to the lower level, and this proposed reg makes that fix.
The example is someone who makes $9 million in gifts that are covered by the credit during the period when BEA is $10 million but dies after BEA drops to $5 million. This individual’s credit amount at death will be treated as equal to the credit used (credit on $9 million), not the smaller credit on $5 million that is generally in effect on the date of death.