OnePlus' president for the Chinese market Li Jie confirmed that the OnePlus 11, Ace 2 and Ace 2V smartphones would receive 4 major Android updates and 5 years of security patches. That means the OnePlus 11 will be eligible for the future Android 17.
That puts OnePlus alongside Samsung and Google with the longest support for its flagship models. But keep in mind that the information comes from OnePlus' president of the Chinese arm. So we still need to hear something official from the global OnePlus representatives.
As per Li Jie, this would cost the company CNY 100 million or nearly $15 million to maintain its phones for more than four years post-launch, which sounds like quite the commitment. We will see if this includes the global variants of OnePlus' handsets.
Source (in Chinese)