I am neither a hater or supporter of Donald Trump so please don't take this as some "political take"
Trump, as everyone would agree, is at least a little narcissistic (which I'm not saying is a bad thing; I actually like and respect his confidence), which means he'll be very, very concerned with his image, his legacy, and how he is ultimately remembered as President.
Thus, I actually think its a lot more likely than not that he DOES lead the push towards the legalization of sports gambling in this country in the coming years, as a strong positive towards his legacy. It's attainable, and as a result, he's going to make it happen as a way to be remembered in a positive light.
I have no doubts about thi, especially given his history with his casinos and the extra potential "incentive" of being able to stick it to sports leagues who prevented this, and from him making a lot more money at the time, during his days owning casinos