Of the three films, I think only The King Of Comedy would remind people of Hinckley in any significant way. So if there's a backlash against Scorsese from Reagan dying, my guess is the film doesn't get made, or, as you seem to suggest, done in such a way that makes it seem like Scorsese is grappling with the issues raised, in a "socially responsible" way. Maybe the De Niro character is portrayed as more unambiguously evil, and the script avoids any suggestion that he might have a point about the arbitrary nature of TV gatekeeping.
And if Scorsese is known in some philistine quarters as "the man who killed Reagan", he probably doesn't get the backing to do an iconoclastic Jesus movie in the late 80s. Cape Fear might not get made either.
Maybe Scorsese does a more straightforward, pious version of the life of Christ than "Last Temptation." After that I think his career would pretty much be the same. Though Cape Fear not getting made would have important ripple effects because it was a deal between Scorsese and Spielberg that got Schindler's List made: Scorsese gave Spielberg the rights to Schindler's List, while in exchange Scorsese got to make Cape Fear. And it was the financial success of that film which allowed Scorsese to get the funding to make The Age of Innocence, and it was the financial disappointment of that film which contributed to Scorsese's desire to return to making mob movies with Casino.