Yes, I don't see why they wouldn't. If everyone is wearing masks then the likelihood of transmission is lower. Also the viral load of any transmission may also be lower, which could improve the outcome.
The herd immunity is 2/3. If say 1/3 of population has already some pre-existing immunity (from casual reading of Internet it looks that some noticeable share of population does have it for Covid and it seems larger than 1/3) then the total infection rate until herd immunity is reached is 1/3. The Spanish flu hit 30% of human population for example.
So, for Moscow 1/3 is 4M. They already got 0.5M cases and currently is having, despite the tight masks/gloves/partial lockdown measures, 7K/day cases. I don't see why would it slow down, and if anything i suppose it will only go up in the coming several months. Thus in the year they will have a total of 2.5M of officially registered cases. If one adds non-detected cases one can see that it is would be in the ballpark of 4M. I.e. herd immunity, end of pandemic, masks or no masks, lockdown or no lockdown. Basically like Spanish flu scenario, and i personally just don't see how the numbers can play differently.
Global effects are the sum of local effects. I don't see how you can simultaneously believe that a mask lowers the local transmission rate without effecting the global transmission rate.
1) A slower infection rate prevents or at least helps with “flattening the curve,” that is, avoiding overwhelming health care systems, which impacts both COVID and non-COVID patients
2) A lower initial viral dose seems to lead to better outcomes (lowers mortality rate)
3) We are seemingly within reach of effective vaccines
2) Would be a win if it is so. I haven't yet formed even a barely informed opinion. It looks like a new development though, and I don't remember such thing mentioned about other viruses.
3) which is why i put the numbers only up to a year ahead as any mass vaccination doesn't seem happening earlier than that.