Heh, now I remember reading "Ultegra shifters". My Campy brain defaulted to avoiding the asplosion from putting Shimano on an Italian frame, lol.

You are correct. Shimano spacing is the same for 8, 9, or 10. The chain width will differ, but any 8 sp or 9 sp RD will work on an 8 sp cassette. You might have some trouble getting an 8sp RD to give enough throw for 10 sp, depending on cage length.

If you change rear wheels, might as well go 9 sp and get all your group has to offer.