I would love to combine two of the best things in cooking, deglazing with a fonds or wine and my cast iron skillet, which I have been seasoning for a couple of months now. My concern is that the seasoning might remove the seasoning from the skillet. Could this happen?
If it's properly seasoned, and affixed well to the pan, there shouldn't be any problem.
In fact, it's what I typically use to clean my pans even if I'm not making a sauce.
If you're reducing a sauce that's highly acidic, you might have cause for concern, as you don't want to have acids in the pan for long periods.