September 2 we will be down to the Final 4.
September 9 we will be down to the Final 3.
September 15 is the Finale, yes Wednesday, and it will be following the premiere of this season's Survivor.
All of that into consideration, they will not do another double elimination just to bring back a house guest who was already eliminated, in my opinion.
I personally don't think Julie meant that a house guest will come back when she said "expect the unexpected" in the Big Brother house. I personally think she was referencing the strategy of Matt who thought he was safe, he didn't expect the unexpected, which in his case would have been to expect he wasn't safe, instead of throwing the competition.