Do not water! The plant is dormant, so it does not need water or fertilizer. The parent bulb (the largest one) is still nice and plump, so it is doing fine.
Personally, I do not cut the old roots when I repot a catasetum. They will help anchor the plant in the pot until the new roots get well established, and they also may retain some diminished ability to take up moisture when you start watering later. You can leave the bulb loose, without media, until you see a new growth start. Then pot it up so that the newest growth will have plenty of room to expand. Don't water until the new roots are 2-3 inches long.
Have you read the culture information on Fred Clark's website?
Sunset Valley Orchids - Superior Hybrids for Orchid Enthusiasts