His approval ratings keep on hovering in the 36-40% range, and his disapproval in the mid to high 50's.
His approval rating needs to drop below 30%, and his disapproval above 70% for any meaningful attempt to remove him from office.
While I think it's highly unlikely he actually will resign, at this point that's our only hope of him leaving office. Unless some one of the many investigations uncovers something so criminal that, were he not President, he'd be subject to immediate arrest.
Keep in mind, that the line of succession totally sucks in terms of who the next. Here's a link to the Wiki article: https://en.wikipedia.org/wiki/United_States_presidential_line_of_succession
After the Vice-President, comes the Speaker of the House (Paul Ryan), then the President Pro-tem of the Senate (Orrin Hatch), and then the succession goes through the Cabinet, starting with Rex Tillerson, Secretary of State. There is not a single person on that list who wouldn't be as terrible a President as Trump, only in different ways.
A President Pence isn't going to appoint a bunch of moderates to his cabinet. Nor will a President Ryan.
What we should hope for is something that would allow someone who isn't a right-wing nutcase to appoint an entire new cabinet. And that's not very likely to happen before 2020.
I suppose there's a distant possibility that some incredible scandal could cause all of those people to resign, but I'm not holding my breath.