Two new versions of Apple AirPods will go into production in the fourth quarter of 2019 or the first quarter of 2020, according to a research note from TF International Securities analyst Ming-Chi Kuo.

One model will have a similar design and price to the current version of AirPods, which costs between $159 and $199. The other model will have an "all-new form factor design at a higher price." The new wireless earbuds could launch during the fourth quarter at the earliest, according to the research.

If Apple releases a more expensive and redesigned set of AirPods, it could give a significant average sales price boost to Apple's most successful new product in years. Apple does not release sales data for its headphones, but independent analyst Neil Cybart previously estimated that 40 million pairs could be sold this year. (Apple sold 217 million iPhones in its fiscal 2018.)

Kuo's estimate for AirPods sales is even higher: 52 million shipped in 2019 and between 75 million and 85 million shipped in 2020. He's bullish on demand for AirPods.

From Tuesday's note:

We expect Apple will likely launch two new AirPods models in 4Q19 at the earliest. One is the all-new form factor design at a higher price. The other's outlook and price will be the same as the current model's. ... We are positive on the demand for AirPods and Apple's leading position in the true wireless stereo (TWS) market, and estimate AirPods shipments will reach 52mn and 75–85mn units in 2019 and 2020, respectively.

Apple released a slightly updated version of AirPods earlier this year with a slightly faster chip and wireless charging support.

It sounds like the forthcoming redesigns will be more substantial. Kuo writes that Apple will use a new kind of internal design called "SiP," or system-in-package. His research is well-respected and targeted at investors in the companies that supply Apple with parts and assembly services, and he said that Apple could revamp its AirPods supply chain with these new models.

When Apple's new AirPods are launched, they could face stiff competition. Microsoft and Amazon are rumored to be working on wireless earbuds to take Apple on.