Actually, it will be interested to see who will suggest a potential victor a hand in its annexationist policy and prefer to exchange old allies for new to obtain a better future or just survive in case of the success of Gallic campaign. But I expect as much changes as possible.
I mean that the same Bretonia shouldn't last long after another war, when its forces are exhausted and it's home front is getting unable to support the war efforts. So several sides interested in bretonian space may agree on some cooperation and screwing the world together.
That won't be interesting to see "Everyone versus GRN" for sure.