We think... we're not sure. Iannucci is being typically cryptic. Thankfully some other people affiliated with the show are a bit more straight forward.
Chris Addison, who plays "human worm" Ollie Reader and has directed the odd episode, is a good example. He retweeted a post by Simon Blackwell (writer/producer responsible for The Thick Of It, Veep, Peep Show, Have I Got News For You, In The Loop...) two hours ago which read: "Don't forget to say a big "F*ckety-bye" to The Thick Of It tomorrow - the last episode is on BBC2 and BBC HD at 9:30pm."
To be more specific, Addison also retweeted this from Tony Gardner yesterday "Last ever episode of The Thick of It on on Saturday, 9.30pm, BBC2. A pleasure and an honour to be part of it."
Speaking to The Guardian, writer Sean Gray said: "It's a shame to stop but it also makes sense because hopefully we haven't outstayed our welcome. It's great to leave at a point where people are hopefully wanting more. That's the best way."
Iannucci, however, is deploying a glimmer of hope which I'm choosing to cling to. Also speaking to The Guardian, he said: "It's definitely the last series. I've known from past experience to never say never." Mixed messages, yes, but I'm going with the second sentence.
For the realists out there; there is plenty from Innaccui to look forward to, namely his big-screen adaptation of Alan Partridge and the second series of HBO satire Veep, starring Julia Louis-Dreyfus. In the meantime, there's always tomorrow night's finale to absorb, not to mention repeated viewings of last week's hour-long 'Goolding Inquiry' special, which was one of the finest pieces of television this couch potato has ever had the privilege of watching.