Well this is how creators stated it. Them walking into portal represents starting of their relationship. So comics will probably cover everything after said relationship started like kissing and... holding hands!
My favourite Monogatari series(because there isn't many scene with that damn annoying Araragi) and my favourite pairing(more than Hanekawa X Senjougahara).
I do hope that Kanbaru gets an actual girlfriend at some point. I'm just sick of seeing her getting cuckolded by Senjougahara, and all of the weird flirting with Araragi. It's unlikely to happen, but I can dream.