I've seen a few reports on the internet that Apple is gearing up to sell 50 million Apple Watches next year. This seems to be based on leaked figures from LG.
To me these numbers seem insanely high. Apple has sold about 160 million iPhones in the past year, and is likely to sell a similar number this year. There is almost certainly going to be high demand for the iPhone 6 and 6 Plus so sales this year might even reach 200 million.
The Watch is an accessory that only works with an iPhone and will cost significantly more than the upfront cost of an iPhone on contract yet unit sales of the Apple Watch will be a quarter of the iPhone sales?
As tempting as the Apple Watch might be, a starting price of $349 (and probably much more) is a lot of money. I would say that Apple would probably be happy with selling 10 million Apple Watches next year, especially if they are the more expensive versions.