So, judging by Ozpin's words at the end of Ep. 5 and the focus on Pyrrha, we can conclude that she's most likely to be the "guardian" he has in mind. Let me explain why this is a VERY BAD sign for her future:
RWBY focuses on team RWBY, and therefore, they (especially Ruby) need to be the heroes if RT doesn't go into some odd avantgarde territory of storytelling. So what that means to me is that something very, very bad is going to happen to Pyrrha. She will likely be faced with some impossible challenge that will break her, fail Ozpin's expectations, or simply be killed off (If that happens, I feel for you, Arkos shippers ;( ), leading to "someone" (probably Ruby) taking her place as the guardian.
Now, on a somewhat happier note, the first of my three guesses could possibly lead to a kind of role reversal in the Arkos - relationship, with Jaune taking care of Pyrrha at a time where she desperately needs it. It would be a good basis for some drama, without going into suicide inducing levels of depressingness.
- Tiberius