Here is how I see things proceeding after the mid term selections. I think the House will go to the Democrats, barring a substantial event. There is a small chance the Senate will shift as well. In the short term, Republicans will rush through as much as they can during the lame-duck period.
Come January, additional indictments are likely (maybe even by November). Democrats will initiate investigations into a variety of issues being suppressed by Republicans. As more information comes out, Trump's approval will take a hit, even among diehards. Trump will no longer control the agenda.
Impeachment will not occur before the year is out (investigations take time). That could be stepped up considerably if Mueller issues a report. His indictments already provide a clear roadmap. His report will be even more detailed. If Trump issues pardons, impeachment will come even faster.