My big screen tv cost £1,350. I've had it for seven years. So it's cost me around £200 per year, i.e. less than £1 a day. When it finally dies, I won't be asking Sony to replace the internals so I can reuse the outside.
People who can afford £10,000 Apple Watches are, I strongly suspect, the kind of people who are really not that cost conscious. I don't think they'll be furious if, in two years time, a newer, better, different-looking one comes out. They'll just buy that one.
The Edition is aimed at people who don't look at money like the rest of us do. They might think to themselves "it'll last two years, so that's five grand a year". Or, more likely, they'll spend the money and barely notice the cost. They will have forgotten about it in two years time.
People who worry about the Apple Watch 2 being better and wondering if there'll be a special deal to just replace the internals of an Apple Watch 1 are almost certainly not the kind of people who'll be buying an Edition. If your budget is that tight, you really shouldn't be buying ten thousand dollar wristwatches.
Edition buyers are the kinds of people who go to clubs and ostentatiously order £500 bottles of champagne. They don't ask for refills. The money's gone and they don't care.
People who want an expensive watch and want it to last for 20 years wouldn't even consider an Apple Watch. It's a wholly different product. It's disposable jewellery, not an heirloom.