Given all the hints and voice lines, there's no way they won't at least be involved I think, but I imagine at this point they're giving them a chance to make an impression before putting them together and saying "now kiss." Remember, Garen doesn't even consider the idea of listening to other nations to be worthwhile, while Kat is mired in trying to earn her father's respect/finding said father. They're stuck in two very closed mental states right now, focusing on a single thing that could ultimately be harmful to them. Giving them time to set up these character traits now can add more conflict later when, say, Garen finds himself interested in someone from one of those outside nations, or Kat begins to wonder if she'd need help from an outside source to find her father or something like that.
I don't know, I'm just spitballing here.