Masks imposes such a hurdle on spreading that, even in the (incredible improbable) event that some virus strain gained a 20% more effectivity of transmission through masks, the mask itself would be restricting 99.99% of the spreading. Overall it means that in place of 1 transmission each 10,000 contacts with mask you'll have maybe 2-3 transmissions of this super-virus even with masks, but 5,000 transmissions without masks.