We have a somewhat similar issue. We bought into our area for its rural nature, and have already attended one zoning meeting to argue against allowing subdivision of a local 100+ acre farm for eventual housing development. Even though zoning in our area requires no more than 1 house per 3 acres, we still think that 33ish houses are more than we are interested in adding to our area.
That said, we did purchase an "insurance policy" of sorts by purchasing a property that borders to watershed preservation land that can never be developed. It was the best we could do in our county. Honestly, when the sprawl of our area already covers 4 states, we'd have to move another 2 hours west in order to have enough distance from the current sprawl. It just is not practical.
I guess I really don't have any good advice. We rolled the dice that our county zoning, our vocal neighbors who value the rural nature of area as much as we do, and the slow housing recovery will at least fend off most of the sprawl for a while. But it may be inevitable, and we'll have to adjust out plan if it ever gets too close for comfort.