Series 4 and 5 total 13 episodes that will be split in two, with series 4 airing 7 episodes early next year (probably in January) on ITV, while the back 6 episodes that make up series 5 will be aired later on UKTV's Watch Channel probably mid-2011.
Primeval's executive producer Tim Haines said of the "bigger and better than ever" series (the episodes reportedly cost more than £1 million each to produce) that:
"The new series is, by far, the best yet and we're really proud of what we've done. The non-stop action and the cast of monsters and creatures in each episode are going to blow audiences away and the fans are really going to be excited and amazed."I really, really like Primeval. The popular sci-fi dinosaur show is one of my guilty pleasures along with Merlin (which I've currently discovered - shame on me for discovering it so late I know) and Doctor Who and I'm looking forward to see what the newest seasons will bring.
In the meanwhile you can read a report here and another here about the series.
[via Den of Geek]