The next-generation AirPods are expected to be released sometime in 2021 and according to Ming-Chi Kuo, a renowned Apple analyst, the pair will adopt the more advanced SiP technology instead of the current SMT tech. For the record, SiP stands for system-in-package chip solution while SMP means surface mount technology.
SiP allows for more components to be crammed inside smaller space, similar to the AirPods Pro. The current design of the AirPods Pro uses SiP and the custom H1 chip is handling noise-canceling, Siri commands, connectivity, etc.
It’s still unclear what exactly that means for the end-user but it will likely enable more advanced features and most probably, smaller form factor.
Source: Gsmarena