A second-generation Apple Watch is predicted no earlier than mid-2016, and will likely feature a thinner size and better performance, according to a Cowen and Company research memo based on a recent tour of Asian suppliers.

The Cowen forecast calls for Apple to ship 18 million Watches by the end of 2015, but at least 45 million in 2016, added analyst Timothy Arcuri. Figures for next year may actually be too pessimistic based on the strength of 2015 data, he suggested.

The original Apple Watch shipped on April 24. Should the Cowen predictions be accurate, Apple's follow-up could arrive in May, June, or even later.

It's unclear whether Cowen's claims about the features of the device are purely speculative or based on research. Very few rumors about a second-gen Watch have emerged so far, such as one from July claimed that the new hardware would retain roughly the same external design, but make more room inside for a bigger battery.

Apple often sacrifices potential battery gains for thinner designs, but might also be inclined to meet demand for a wearable that can last 24 hours or more on a single charge. Few major smartwatches can reliably run more than that, and often depend on technologies like e-ink or disposable batteries to do so.