“When making decisions like this, I don’t think about what conditions are were I to ship today — I think about what conditions will be like when I actually do ship, and I think about conditions six months out as we do support, testing, and maintenance releases.”
Good advice. And remember, very few developers actually ship on time. Even if you think your app is going to ship before the next major version of the OS does, your app will probably be late. More people will be able to run it than you first expected.