TSMC is aiming at 2024 for 2nm, they're the market leader and they reportedly started research back in 2019

https://wccftech.com/tsmc-2nm-research-taiwan/

https://wccftech.com/ssmc-mass-produce-2nm-2024/

now a consortium of runner ups not only hopes to catch up, but plans a parallel release of a new node size, while starting later, while starting with less know how.