About the ''future visions'', I think most of them are meant to show something bad happening to Hiro, Yana, Yuki and Sachi, some kind of tragedy, and leaving just Kakeru and Touko behind. I'm not talking about just the two of them in that snowy scene (which represents death?).
I think it's pretty strange that they are walking on train tracks. It's possible that Touko doesn't want them to go, and she probably tried to convince them to do so.