User blog comment:G0LD3NF1RE/Skyrim Dawnguard DLC/@comment-4644719-20120503025933/@comment-5060344-20120504205849

Same applies for the Stormcloaks, Ulfric and Galmar both say that darker times are coming to Skyrim and mention training armies to fight the Dominion. So I guess either the Legion or the Stormcloaks could work in that scenario. But I can't see that happening, but yes, speculation is fun.