They'll all fail because there simply is no mass need to drive sales.
I wear a Nike Fuelband. It's not really a "smart watch", but it's a nice reminder I need to get up and walk. I can hit a button and get a semi accurate reminder of how active I've been for the day. It pings my phone when it needs my attention, and in since it's not my phone I can wear it to the gym and let it's accelerometers rate my activity. I know, I could ask myself if I've exercised enough for the day, but when I'm deep in a programming puzzle, I need the nudge.
Why do I bring up the Fuelband?
It would be great to have a Fuelband that can do calendar reminders, and maybe some sort of digital wallet thing. Maaaaybe read only interface to my text messages. My needs aren't extreme. I think that's why most wearables have fallen flat. A lot of the Android wear smart watches have features like cameras, microphones, voice control, blah blah blah... So much crap I don't need, that I'm paying for, and that will run the battery down. I want an accessory for my phone. Not a watch computer onto itself. I don't need a duplicate of every feature I have on my phone. Just tell me what room my next meeting is in so I don't have to take my phone out of my pocket.
Wearables are in an unnecessary arms race right now. What wearables need is a simple set of features done well, and done in a compelling way. That has Apple written all over it, but we'll see what Microsoft brings to the table as well.