if they'd go for an every other 4 year schedule, say City A hosts in 2018 and then in 2026. City B hosts in 2022 and then again in 2030. City C hosts in 2034 and then again in 2042, City D in 2038 and then again in 2046, and so on and so forth. That way you can reasonable get multiple uses out of the venues without unreasonable maintaining the venues for decades.

I do like the idea of choosing 5-6 permanent sites. No more of this hosting the winter Olympics in coastal cities with slushy snow, or the summer Olympics where the beach volleyball players are wearing long sleeves to stay warm.