Yeah, Damon said they still had 8 weeks of shooting left. If they start 1 July they can finish filming by end of August. That leaves almost 4 months for post-production. And Ridley wouldn't have been idle all this time either, I think he's already got half the film edited and may have started work on some of the visual effects shots and perhaps the soundtrack already.
Bit of a rush towards the end but do-able, I think.