They'll either just set the game so far in the future they could not mention it, or they could have Elisif as High Queen, either way.
It's telling that she's the only jarl who remains in her position, they wouldn't have done that for nothing, especially as they went to the trouble of removing a quest where she gets killed off. Not all Stormcloak jarls approve of Ulfric, so it's entirely reasonable that there's such a disagreement that Elisif remains in charge and 'High Queen Elisif' is who we hear about in the next game.
I doubt it'll be the truce, as the failure of the Stormcloaks equates to an Imperial victory, and Bethesda's not risking that great a need for increased moderation fan rebellion.