If the midterms don't go well for Democrats, we may not see this report for years, if ever. Mueller reports solely to Congress, not the public. It'll be like handing the report on crimes to the criminals that committed them if the GOP retains control.
In any case, we already know they conspired with the Russians to affect the election from the Trump Tower meeting alone; not even getting into all the back channels with Flynn and Kushner, Trump publicly calling for the hacking, the Seychelles meeting, numerous secret meetings with Kislyak, Carter Page going to Russia, Cohen's goings on there and Trump's Russian business dealings he lied about, and so on and on. It's merely the extent that will be new.
What we already know should be enough in a sane world.