Taking 1 workout away from 2 or 3 in a week, yes, you might sacrifice some size. Taking 1 away from 5-6 per week - probably not. There are plenty of things you can do to keep your size. I think lifting is key. Don't neglect any bodypart at all. I would say add the cardio in addition to your lifting. If you don't have time, shorten your work so you can combine lifting days. When I am really trying to drop fat and am doing heavy cardio, I sometimes do full-body circuits w/no rest. The lifting becomes a cardio workout on its own, and it may be a new enough stimulus that you actually grow from it. It's a different feeling to do a whole body circuit. I don't feel like I taxed any one body part in particular, but I can feel quite exhausted afterwards.
Your diet is also going to play a big factor, perhaps the biggest. Kepp the protein high and try dropping carbs. This preserves muscle very well for me and also helps me drop fat. Pay close attention though, as it might no work for you. Don't be afraid to change the game plan if you feel like you were really sticking to it, but it wasn't working for you. If you are lying to yourself and not really doing what you were supposed to, you will never know if it worked for you or not.