Both "a saída é a direita" and "a saída está à direita" are usual in Brazil. The second one is told to you when you leave the theater, for example.
My feeling is that whenever you can say "estar localizado" (to be located), you can omit the word "localizado" and say just "estar", especially when explaining something. Eg: the building is located across the street = "o prédio está (localizado) do outro lado da rua". "To be located" in Portuguese needs the verb "estar", not "ser", even for permanent things. Eg: Brazil is located in South America = "O Brasil está localizado na América do Sul".
We often use "estar" if "we" are moving (or, of course, if the thing we refer to often moves).
It's very rare to use it otherwise. (Of course, that does not affect "estar localizado", which is always good).
- We walk around and find nothing, then we ask "onde está a saída?"
- We just got up from our seat and ask to the person beside us "onde é a saída?"
- We are preparing for a trip, we ask "O Brasil é muito longe?"
- We are in the middle of a trip, we ask "O Brasil está muito longe (ainda)?"