We can only guess that Marco and Star were going to say good bye to each other and that Eclipsa's scene were the magic in the crystal wad starting to fail was going to place her as the next danger.
Nefcy was a big fan of open endings and magical girls (particularly sailor moon) so I'd not feel surprised if her ending was a mix of some animus and mangos endings, I mean come on, even her actual shitty ending is a rip off of many magical girl ends where they have to "sacrifice" their powers/magic to save those they care about. The big, massive, notorious difference between Star and pretty much any magical girl is that when this sacrifice comes they actually suffer, they feel bad for it and they feel like they are losing something important in their lives. Making "the guy" that "love of their lives" almost meaningless in comparison for that moment.
Star failed not only as an autist, a girl, a feminist, but also as a magical girl.