Let the EPA try. A good excuse to abolish them when we take over.
That is not likely in my opinion. Congress could however, quickly remove CO2 and GHG's from the EPA's authority under the CAA.
That is a more plausible outcome if the fit hits the shan. Unfortunately, I expect that lititgation on the issue will be the likely route which will give the administration cover to say "we are doing something" and Congress the cover to say "it is working through the system" without pushing either to take responsibility and fix the problems it will cause.
Businesses and the economy are likely to suffer from the regulatory uncertainty, but not as much as regulation by the EPA under the CAA.
I believe EPA is counting on litigation forestall implementation actually. If they weren't - they wouldn't be trying to twist the CAA with their "tailoring rule" which so obviously disregards the specific language in the CAA that it is laughable and I'm not even a lawyer.