I think they might end up together, just going by the intro with Sang Soo pursuing Soo Young throghout the different locations. I take the jelly figures to represent him and Soo Young. He spends the majority of the time pining, walking steadfastly behind her which symbolizes his lingering feelings and attachment to her before she finally looks back at him. I think in the end she'll stop running and face him and maybe the ending will be open-ended as they figure out where to go from there.
I do want them to end up together, but it could go either way. Regardless, their current partners aren't their HEA's just because neither seems fully fulfilled/happy. Someone mentioned that the book it's based on has him missing Mi Kyung, having broken up with Soo Young, but I put little stock in adaptations being 100% faithful. Since there's always room for artistic liberty, the ending is a toss-up. How do you think it will end? I look forward to hearing your thoughts.