Mueller is going after anyone with ties to Trump. He’s set up his own version of the FBI. He’ll busy himself for years.
While I agree with most of what you said, I don't think they want to leave Trump in office that long. My guess on the script is for the first trials to start in early 2018 (already scheduled), convictions of those Trump associates plus more trials of others in the summer, then using that to fuel enough Democratic wins in Congress to lead to impeachment in 2019 to include some Republicans defectors.
Hopefully that won't happen, but it will take a strong and unified counterpunch against Mueller to slow it down.