I am more inclined to think that there won't be any solid ending, since the manga is still ongoing, but if there is going to be any pairing implied by the end of the show, I am pretty sure it is going to be NagixJin. Kannagi just falls into that category, and it would seem quite pointless if the main female character is the one to get the short end of the stick.

EDIT: and I am not just saying this because I am a Nagi fan, as anyone should be able to tell.