It might mean more than you suspect. We live in a world of both political extremes and extreme expectations. A lot of progressives and democrats were upset last November because they somehow were hoping for even bigger gains than they saw, or fretted too much that the party of trump retained control of the Senate. Never mind democrats actually had a very good night, with near historical gains in the U.S. House and winning back a number of governors races and state houses too. Hell, even almost holding their own in the Senate with the map they faced was a respectable outcome.
If the Mueller report is what many suspect it is, just a confirmation of what anyone who is paying attention and believes in actual facts already knows, then some on the left will be greatly disappointed. I for one have been saying for well over a year now no one who is related to trump by blood or marriage would be indicted, and that looks like it is true.
Just like trump repeating lie after lie after lie very easily trains his minions to believe him to be telling the truth, the nightly all trump is bad all the time "reporting" on CNN and MSNBC has led too many to believe that there was a real chance trump's children, Mike Pence, Hell, even trump himself, may have been perp-walked out of the White House in handcuffs. The instant this report is made public (however much of it sees the light of day) all the previous indictments, guilty pleas and convictions that resulted from Mueller's work will be nothing but a memory to most people. All we may see is lots of people saying "two years for THIS?"
That let down may be more damaging than you think, especially if it dampens and derails enthusiasm among people on the left. That is the rub I have been worried about all along. If you're going after big game, you better bring it down.