The thing we don't know is that Maracana issue can open a precedent for future host cities make two stadiums logistic as Rio will do.
If we see it by other perspective, Vancouver (even being an Winter Games) did it first... I don't know how much IOC is interested in a stadium exclusively for ceremonies.
Anyway, Rio will be test for this new way of doing things. I agree with you that if Maracana-two-stadium-thing won't work well, this will be never repeated and Rio will go down in history as the worst ever, but think otherwise, if logistics works well... Maybe a new standard can be set.