They should still be there - sauropods are known to live past 40, making them the longest-lived dinosaurs that we know of. Rexy might have made a pass at them if she was feeling brave, but you'd think she'd have munched through the Parasaurolophus, Triceratops, tardy Gallimimus and excess goats first. Or they could have gotten sick, though the DX disease hasn't been introduced in the films.
I remember people mentioning they heard Brachiosaurus calls at a couple of points in Jurassic World, but it's not in any of the documentation, so shouldn't be on public display.