Congress cannot reclaim its ceded power. Initially, Trump won’t have it, either. He has to take it from the Agencies. The Executive IS the government now and it will be a contest between the President and the Departments and Agencies as to who exercises that power. A Democrat President, being part and parcel of the Ruling Class that includes the Agencies will slide right into the headship of the Executive. Trump has to kill the Agencies or become a cipher.
“The Executive IS the government now”
What happened over the last 8 years (last 16 really) in Congress ceding power to the President won’t matter. At all.
The day Trump takes office, Congress aided by the media, the Republican establishment and the entirety of the Democrats will rediscover how much power Congress has to rein in the President. Everything he wants to do, they’ll find a way in Congress to block it. Bank on it.