Answer:
I know they will do a primeval series 4 they have to.
The reasons are:
1. Connor and Abbey are still left up in that tree in the cretaceous peiriod.
2.Danny is still stuck in Site 333. http://primeval.wikia.com/wiki/Site_333
3.Sarah and Captain Beker are still left on the outside of the Anomaly.
So I'm pretty sure that they are going to do a series 4 because my life depends on it... PRIMEVAL ROCKS!