You are correct, the CDC issues recommendations and it is up to each state to determine if they will enforce those recommendations. A state can go both ways, they can be like Florida and say we don't care, we are 100% open. Or they can be like NY and say we are not lifting indoor mask rules for vaccinated people anytime in the near future.
Whether this tour happens, will depend on each states capacity rules. I have tickets for Citifield in NYC. On May 19th, stadiums in NY can go to a vaccinated and unvaccinated section with vaccinated at 100% capacity and unvaccinated at 33% capacity. In this format, the concert would either need to be postponed, canceled or tickets refunded and resold. Anyone who lives in the NY area can tell you, it is unlikely that Andrew Cuomo will open everything to 100% capacity by Aug 4.
I agree with you that alot can change in 2 months, but I would imagine it is a logistics nightmare to try a rearrange a stadium concert in 2 months. Clearly the promoters are banking on everyone opening to 100% capacity.
I think there will be some venues that will be allowed to have the concert and some not. So what do the promoters do? Do some shows go on and others canceled or postponed? Or do they cancel or postpone the whole tour? I don't know what would make more sense from a promoters point of view.