You can't undo rust, so reversing the damage is not possible. I wouldn't worry too much, unless your skis were submerged in water for several days, the amount of ski edge that you will lose is probably less than what is taken off during a tune.
Store the skis in a dry (air-conditioned) place during the summer. (Not your garage or basement.) Maybe take some light-weight sandpaper and gently brush off the rust (be care of not sanding the bases). If you're really worried and you have access to hot wax, you may want to seal the edges with a layer of wax to prevent further oxidation. (You or the ski shop will need to scrape the wax off before you get the skis tuned.) The last step is probably overkill and can be messy.
1. The first (and more expensive): I take the skis to a ski shop and have them do a end-of-season tune which also includes extra wax over the edges. Then I put the skis in their Gritz Guard and set them aside in my closet, not the garage or storage room. The good side is that the wax will last and the edges will be as smooth as ever. One could say that there is a bad side as I will take them again to the shop before using them in teh beginning of the season, but I always take them to a professional anyway to do at least a binding release check and also get them ready for the season.
The second and cheaper alternative: Toko sells an edge guard that you can apply from a tube just like the shoe polish applicators. It works but not as effective.
Some of the citri-strip fluids will actually accelerate rust if you try to clean rusty skis with them (e.g. Goo-Gone on '90s Elan MBX edges). Short of ski-specific chemicals, try ammonia Windex to clean, silicone spray to preserve.
BTW, try blue Windex instead of water as a cutting fluid for DMT stones when the edges are really rusty.