The initial bill passed in the House of Representatives did just that, by phasing the estate tax out over a period of time. However, the Senate version of the bill was more cautious and just changed the exemption limit, while keeping the estate tax in place.
This was necessary because for procedural reasons, tax reform could only increase the federal deficit by a set amount. Repealing the estate tax entirely would have put the Senate over that amount. The two chambers reached a deal on reconciling their tax reform bills.
The final version of the tax bill kept the estate tax. However, it nearly doubles the current $5.6 million exemption to $11 million. That means that an even smaller percentage of estates will be subject to the federal estate tax in the future.
An estate planning attorney can advise you on any upcoming changes.
Reference: Business Insider (Dec. 14, 2017) "Republicans have a final deal on their tax bill — here's what's in it."