I expect it'll be a yearly update. Howcever, I think it'll not get a redesign every year/two years. I'll be more like the Mac where the design is updated every 3-4 years. However, I think 'bigger' updates for the Apple Watch will be times to be not in a year when there's a new iPhone. Therefore, when there's an iPhone 'S' version, there'll be a fairly big Apple Watch update, yet there'll be a smaller one where it's a big iPhone update.