Sarah Tew/CNET

Fitbit, the company behind the world's most popular wearable devices, may have big plans for the remaining months of 2016. So far this year, the San Francisco-based company has already released two new trackers: The Fitbit Blaze smartwatch arrived in March for $200, followed by the Fitbit Alta activity tracker in April for $130.

Now a recent filing with the US Patent and Trademark Office suggests that Fitbit may have two more new fitness trackers in the works. As first reported by blogger Dave Zatz, Fitbit has filed a trademark application for the Fitbit Flex 2 and Fitbit Charge 2.

Both trackers are primed for a refresh. The original Flex was released in May 2013 for $100. The wrist-worn fitness tracker measured steps, distance, calories burned and sleep. The Charge debuted in November 2014 for $130 and added a small OLED display for viewing fitness data right from the device.

A Fitbit spokesperson declined to comment.