Well, I suppose he could start dating Ran now that she's available.
Too soon?
Though art evil Nezchan... :p
(although I did choke on my tea when I read that)
I suspect there will be a tearful but very frank confession just before Keiko leaves, one that makes it unmistakably clear how Ran feels, forcing Keiko to seriously consider what she has subconsciously avoided admitting to herself so far. Cut forward until after her assignment, and she will have sorted out her feelings, hopefully returning to Ran to confirm that they are mutual.
Then again, I tend to try to be optimistic...