I can't see there being any significant damage to a set of rotors over a few months of Michigan winter...it will be very dry, so not exactly a haven for rust. My dad's Camaro sits throughout most the year (very rarely driven) and the rotors never even rust. Unless it's being stored outside I just don't see it being an issue.
If anything, put a light coat of oil on the rotors, then wash off with brake cleaner before you drive. Plastidip sounds like a real pain in the ass.
Hatch Nation #29