Well 2009 was a once in a lifetime monumental moment.
The only thing that will ever come close to Obama attendance will be whomever our first woman president will be. (Or first gay president?)
At this point even George Bush Senior will have had a larger turnout in 89.
Just because Trump won, let's not forget the fact that he was still one of the most-disliked candidates in history. I wouldn't expect a big turnout.
What if it was a republican woman?
Trumps team was talking upto 800,000 people while Trump in usual bullshit mode was talking potential record setting crowds etc.