Basically what I meant was kinda of like we saw between Star Wars Episodes II and III and also between Star Wars Episodes V and VI, where the plot doesn't seem quite resolved in the first set like they kinda did in films I and IV but left films III and VI to resolve it.
(In the II-III, it was the Clone Wars, in films V-VI, it was the whole "No, I am your father" thing.)
Anyway, the best spot for a cliff hanger is basically one where they are older and it could have something really dark happen at the end of the second to last film and leave a great urge from the fans to find out how it's resolved (It brings in the $$$ and makes us happy so why not?) and then, in the very last film, resolve it and finally show the next generation of dinos, perhaps learning how the characters got to the Great Valley and all that and their many adventures and stuff, kinda like hinted at in the end of the very first film, only we'd actually get to see it happen.