Speaking of phasing out hardware, I wonder if the Series 0 Apple Watch will be able to run watchOS 4? Apple is usually great about making sure their products continue getting upgrades for a long time, but first generation hardware is usually an outlier. Average iPhone gets four major iOS versions over it's lifetime, but the original iPhone only got three. Same with the iPad, original only got three major versions (If you include iOS 3.2 as a major version), but iPads are hardly ever dropped off of support with major OS versions.
I think it would be risky for Apple to say that the Series 0 won't be able to run watchOS 4, but they could easily point to the Series 1 as the low end model to get for upgarde support. They learned a lot between those two generations, and the Series 1 could probably handle watchOS 4 a lot better than the original Apple Watch could.