It’s been 20 years since Apple has promoted the upgradeability of their products. Back in the 68K to PPC transition, Apple sold computers which touted upgradeability as a feature. Apple even made some PPC upgrades (I have one in a Performa 636CD that I keep around.) If I recall correctly, a problem arose when Apple listed a product as upgradeable, but never shipped any upgrades. I don’t think Apple will offer upgrades for the Apple Watch or Apple Watch Sport, but I don’t think it’s out of the question for them to do so for the Apple Watch Edition. If the Edition version of the watch is indeed priced close to $10,000, the question may be “If someone is willing to pay $10,000 for a watch, will they be willing to pay $10,000 a year or two later for a replacement?”. I don’t think it’s out of the question to think that they might be willing to do so. On the low end, if Apple can keep the prices on most of the regular and Sport models under $500, I think there might be no need to offer an upgrade path.
Either way, I don’t think this part of the story will be told until Fall 2015 or maybe even Spring 2016 (when the next Apple Watch is introduced.)