Noting that I'm no stranger to rustproofing measures (thanks again, Ron!) and that I'm utterly meticulous about cleaning my undercarriages and other out-of-the-way areas, my good vehicles simply don't go out in the salt.
If you take the proper precautions (and it's quite an ordeal to do it right...even if you pay a pro to do most of the work) you can keep most any well-built vehicle from rusting out. Get it rustproofed by somebody good (I'd go with a shop that ValuGard endorses), touch up as needed, and then treat all the areas they didn't do with something good (and do it right). Then clean it *meticulously* when you wash (the first and last hours of my washes are always spent on the undercarriage). It oughta be OK in the functional sense.
BUT...it won't be showroom (or better-than-showroom, in case you're an undercarriage nut like I am

) any more. IME, no matter *what* you do, something somewhere is gonna show some sort of (hopefully negligible) cosmetic compromise from the exposure.
Got any areas where they didn't paint the frame just right (I bet you do!)? You'll see some corrosion. Got any chips or scratches on anything down there? Any areas where a nut/bolt's edges have been dinged by a wrench? Sure you do, and anything like that is gonna rust.
It probably won't matter to anybody but nuts like me, but it just won't be *quite* the same if you drive it in the winter, no matter what you do.