Both are interesting questions to consider, I think.

To the first, I honestly don't foresee Ishgard getting a new Grand Company. Much as I like the idea, I'm just not sure how it would fit into the overall story, especially since how the post-2.0 Story has been... "changing" some things, in regards to Grand Companies. If anything, part of me wonders if, in the distant future, they might remove Grand Companies entirely... although I'm wouldn't be *shocked* if we saw a new Grand Company.

As far as being a new starting City-State, I know I'm in the minority on this one, but I genuinely believe so. Ishgard may be a high-level area, but I would bet money that there will be a single zone dedicated to freshly-created characters. I'll take it a step further, and say that it will be a Doman refugee-camp, and that it will only take you to level 15, at which point you're sent to other existing areas to level (for the sake of the Main Scenario for new players wishing to play the new Jobs, but without creating an entirely separate Story).

But hey, what do YOU guys think?