There is absolutely zero chance Trump and Pence both get removed. Less than zero. If both were removed, and Nancy were made Prez, that would likely be the end of the republican party.
I admit it's extremely unlikely, but less than 0? That's some Trump language :P
I'd say there's a 1-2% chance Trump, Pence, and the White House at large is caught with such damning evidence that over months of trials and public exposure, popular opinion sways to ~75% in favor of removing him from office. If that happens, Moscow Mitch will vote to remove, claim that he doesn't like Trump (which is probably partially true) and never did. Don't underestimate how Republicans can change talking points and fall in line and whip the base with the propaganda machine.