Pretty much this. There's a lot more they can do with this plotline than the Siege of Undercity.
It's more likely that the fighting will be around Gilneas and Stromgarde. I'm sure Sylvie will make an appearance, and probably get kicked in the teeth a bit, but I wouldn't count on another plot death. Well... maybe one more plot death to get rid of her val'kyr, but after that...