I don't think there will be marches comparable to the women's marches after Trump's inauguration if he suppressed Mueller's report, for a few reasons:
1) It's something slightly more esoteric. "Didn't release a report" doesn't have the visceral impact of "grab 'em by the pussy", and every day citizens are much less likely to have a MeToo story about someone not releasing a report.
2) There was direct, incontrovertible evidence Trump said what he said about grabbing women, whereas the suppression of Mueller's report would be the suppression of evidence itself. Some who would march on evidence will not march on a lack of evidence.
3) It's been over a year now, and there has already been a severe numbing effect re all things Trump. If the kerfuffle over the size of his inauguration crowd were to happen now, do you think it would be as big news as it was at the time? Given that just the other day he explained away empty seats at a rally by saying that maybe those people had gone to the toilet and that was barely reported, I don't think it would.
4) It's been over a year, there have been plenty of protests, and nothing has changed. If anything, Trump has become worse over time. There will be plenty who have an attitude of "why should I bother? It's pointless".
5) There actually is less point in protesting than there once was. It's not going to affect Trump, the GOP, or policy in any way; everything is reported on already so it's not going to draw attention to anything; and anti-Trump protests hardly get reported on any more, so it's not going to draw attention to the fact that people are upset.
I think Trump protests have peaked, save him doing something like actually getting into a nuclear war with North Korea.