According to a recent research note released by analyst Ming-Chi Kuo, he claims that in 2021, Apple could have a new iPhone in the works that could see Touch ID embedded into the power button of the phone itself. This is a similar style that we had previously seen companies like Sony use, and it looks like it could be adopted by Apple next year.
However, it seems that this is for a lower-end iPhone model that will continue using an LCD screen instead of OLED. Kuo had previously reported on such a device, where he said that the phone will not use Face ID, and now it looks like we know how Apple plans on protecting it. The embedding of Touch ID in the power button will also allow Apple to create a near edge-to-edge design, similar to its current iPhone lineup.
It is unclear if this will be the iPhone SE 3 or if it could be the third-gen iPhone XR, but either way with it launching in the first half of 2021, we still have quite a ways to go before we learn about it. Until then, take it with a grain of salt.