Empire Online reports
that Neil Marshall, director of "Blackwater," is returning to helm the season four finale, which will feature the Battle for the Wall. If that's all true, they may be shuffling the order of events, or Jon's election as Lord Commander may be held off until season five. But I wouldn't be surprised if there's some miscommunication, and the episode is climactic, but not the actual finale.
Edit: Winter is Coming has been told
by its own sources that the report is "not entirely accurate."