The estate tax exemption was doubled under the new tax law. However, it was not made permanent. The exemption is scheduled to revert back to its previous level in 2026 creating a potential issue, according to Wealth Management in "Clawback Under New Tax Law."
The issue is what to do if someone in 2018 uses the doubled exemption to make gifts and uses up their lifetime exemption under the current law, but then passes away after the exemption limits have reverted to previous levels.
The exemption limit to use for the estate is unknown. It is possible that gift amounts over the exemption limit in place at the time the person passes away, could be clawed back into the estate for estate tax purposes.
Instead of deciding how to handle this issue, Congress has authorized the IRS to decide what to do.
An estate planning attorney can advise you on creating an estate plan that fits your unique circumstances and takes the present political climate into consideration.
Reference: Wealth Management (Dec. 28, 2017) "Clawback Under New Tax Law."