Pretty sure it's too soon to tell if there is any reliable correlation. I do think our upcoming flu season will give some good indicators, as like @Julie808 said, it stands to reason (actually, it is fact) that Covid prevention measures would also prevent other communicable diseases. However, data may be skewed by the fact that in the non hospitalized acute setting right now, flu and other respiratory illnesses are not being automatically ruled out prior to Coronavirus testing and that's going to affect the reliability of our reporting systems.

It stands to reason that covid preventative measures would also prevent many other illnesses like colds/flu, but it would be interesting to learn the statistics throughout the year, compared to previous year, to learn if there's been a reduction in other contagious illness.

Maybe Kinsa, the makers of that digital thermometer that records the temps of fevers on a map might have some clues, if overall sickness is going down, even while covid is going up in many regions. Unfortunately, while folks are still getting covid, I think it might be too early to tell if other illnesses are going down. I'm guessing it's still a bit fuzzy.