I'm pretty sure the Apple Watch 2 will be announced in March. However, it may not actually be available until April. Despite the Apple Watch 1 OK sales, it hasn't sold as well as it should for an Apple product, especially one that is a perfect companion to one of the best selling phones in the world. Every iPhone owner is a potential Apple Watch sale but Apple has been unable to capture the hearts of a large majority of iPhone owners. Releasing a new model will inject interest in the Apple Watch product line and hopefully sway more iPhone owners to buy an Apple Watch.
I don't think the Apple Watch 2 will be a major update though. The Apple Watch 1, despite being a get 1 product, is actually a very good product. The Apple Watch 2 will most likely be "evolutionary" rather than "revolutionary" sort of like the S model iPhones that come every other year. The most I expect is a slightly thinner case, better battery, faster UI performance, a few more health features (possible more sensors as well) and the ability to function better when not paired to an iPhone.
Also, as I've already said in another forum on here, Apple's product lineup has grown over the past year so it makes sense for them to keep the same schedule they had last year (both for profit and to prevent consumer confusion):
March: Reserved for Apple Watch and Macbook lineup
June: Reserved for showing OS updates and new features (this year should be quite large with iOS 10, Watch OS 3, Apple TV OS and the follow up to El Capitan)
September: Reserved for iPhone and iPad
October / November: Reserved for new desktop Macs (either a stealth launch or a small event)