Well. Yotsuba won. Nothing we can do about that. Though the series ending pains my heart, I am pained not because it's over, but because the last few chapters feel lower in quality than the others.
Ah well.
On the flipside, my bet's on Yotsuba being second on the left, what with her hands balled into fists like she can't wait to get married. Ichika is the only one out of the quints who smiles as confidently as the center one, the leftmost quint's arms' pose remind me of Nino, Itsuki's become more comfortable and confident and thus is more likely to be relaxed, like the rightmost quint, and the second on the right quint has a somewhat nervouse expression, matching Miku's characterization throughout.
Please feel free to correct me if you think I'm wrong.