There is an easy and obvious way to see who will ends up who...
If you guys seen the intro music scene (I presume you didn't skip it
) you should see it's all about Souske and Kaname. I know, you may say that's because they are the main characters. But, in the end ask yourself why would they not put Tessa together with those 2 in the intro as well? If they were to twist their relationship around?
That's because Kaname is more "main-character" than Tessa and usually main character gets what main character gets.
But I am sure, and not surprise, there may be a scene where Tessa will kiss Souske and etc... after Kaname got capture as a sort of like "misses-feeling", "express-emotions", "deep-mind-thoughts" things like that. You never know, just what I am expecting.
No doubt, Kaname will end up with Souske. If one of them is not killed... hope not :P