The trailer doesn't reveal exactly which couple will tie the knot, but it seems to lean heavily towards Ali Oetjen and American intruder Grant Kemp.
'I hope Grant will propose today,' Ali says to the camera, with a huge smile.
'I want to spend the rest of my life with you,' says Grant to Ali, implying that he is going to ask the question.
The trailer also hints that it could be one of the other couples that end up hearing wedding bells.
Tara Pavlovic and Sam Cochrane are shown exchanging loving looks at the last ceremony, while Jake Ellis can be heard telling Megan Marx that he's 'falling in love' with her.
Jarrod Woodgate and Keira Maguire are also potential candidates for the mystery proposal, with Jarrod being shown reaching into his jacket pocket before Keira starts to sob.
'I can't see my life without Keira,' he gushes.
The first part of the two-episode finale airs on Sunday night.