There are still a couple of famous dinosaur-era reptiles unused. Ichtyosaurus, plesosaurus, archeopteryx, spinosaurus, diplodocus, ankylosaurus, iguanadon, dimetrodon, Parasaurolophus and archelon all have easily recognizable designs and I can see a few of them easily appealing to kids. Allosaurus is a bit like a t-rex, but kids love that design anyway. Concidering the first wave was only seven sets and five dinosaurs, it shouldn't be that hard to create a second series.
A semi-large aquatic base set, with ichtyosaurus, plesosaurus and/or archelon.
A smaller set, with just a sub and one of the aquatic animals.
A small jungle set, maybe even an impulse, with archeopteryx.
A small long-range net thrower and any small dinosaur.
A large outpost on poles that holds some smaller dinos and is under attack by an allosaurus.
A small tree outpost, with a captured archeopteryx and under attack by a velociraptor.
A large helicopter base that is hunting a spinosaurus.
Just some random ideas.
Anyway, the point is that there is easily enough material for a second wave, so it was probably a conscious decision to rotate the theme out instead.