I think this summer is terminated.
No one upcoming film have the appeal of "big event" a la "Avengers 2" or "Jurassic World".
The rest of these movies could be happy if cross the $200M line. We'll don't see another +$300M beast til Christmas...
TF4 was "ok" in the context of this saga, but was the worst movie of the series, i think this will gonna hurt the fifth movie. perhaps under $200M domestic.