I've recently gone to waxing, and chain rotation as well, and it's really nice. Honestly, if you're using a traditional wet lube for your chains, rotating 2-3 chains makes even more sense-- have one (or two) cleaned/cleaning while one is on the bike. I wouldn't worry about your cassette disappearing-- companies are still making 6-7 speed, so 10-speed should be around for a good while.

Next time you go to get a cassette, check out the Shimano XT M771 11-32. It has the exact same cogs as the HG81, but it's lighter, and shifts a good bit smoother. I ran through 2 of them, getting around 9,000 miles out of each.