I'm pretty confident that wearing a mask will have significantly reduced the likelihood of picking up a cold, though I'd imagine other covid related stuff, notably social distancing and pub closures etc will have played a major part. Maybe the medical statisticians will try to measure those kind of things.

But in any case, insofar as people identify mask-wearing as saving them from colds, that is going to encourage them to continue to wear masks. It won't be everyone, but I anticipate that a relatively long consequence of the pandemic will be that mask wearing will have been normalised. Maybe, in the same way you can date a crowd picture by how many men are wearing cloth caps, you'll be able to do the same by looking for masks.