Israel + West Bank (but no Gaza) would still be a Jewish majority, I believe. But that would still probably be untenable. A "one state solution" would presumably lead to civil war.
Yeah, the Orthodox birth rate and the Arab birth rate would balance each other out, I think. However, the growing dependence on the Orthodox would dramatically change Israel in itself.
is that really the case currently? Doesn't the West Bank have one of the highest fertility rates in the world, with Gaza the highest?
Well, Gaza isn't going to be part of the One-State solution, save it being imposed on a defeated Israel after a war. So that's not a factor.
The West Bank has a pretty high birth rate, but the average Ultra-Orthodox family in Israel has at least eight children and they're immigrating to the country in fairly large numbers, so I imagine it'll keep pace.
I fear for Israeli women if Muslims and Ultra-Orthodox become a majority.