OnePlus Android Update Policy

In July, 2021, OeePlus updated and clarified its Android update policy.

Currently, the OnePlus Android update policy is this:

OnePlus flagship phones (including the T and R models) will get three major Android updates and four years worth of security updates after the launch date. This includes OnePlus 8 and all flagship phones released after it.
OnePlus Nord phones and original OnePlus Nord CE will get two major Android updates and three years security updates after the launch date. This includes the original OnePlus Nord, too.
OnePlus Nord CE 2 will get "two years" of Android updates. But company doesn't state whether that will mean two major Android versions or not.
OnePlus Nord N series will get one major Android update and two years of security updates. This includes the original N series phones: Nord N10 and Nord N100.
Flagship phones before OnePlus 8 will get two major Android updates and 3 years of security updates

However, there are some exceptions to these rules:

Despite OnePlus stating that they only provide two major Android updates to their older flagship phones (OnePlus 7T and those released before that), they have gone against that rule with some models. Some old flagship devices have gotten more than two major Android updates. But that is "going beyond what we promised" kind of thing and shouldn't be relied on.
Additionally, there seems to be one exception to all the rules: old OnePlus 7 Pro 5G. The phone was an oddity as it was solely sold for some carriers only and had very limited availability. To this date, it seems that OnePlus 7 Pro 5G only got exactly one Android update. The reasons behind this decision are unknown - and we don't even know whether the company will "fix" the issue at some point down the line.
With phones released in 2022, OnePlus has refused to promise specific number of Android updates. Instead, they state the years they will promise to deliver updates. So, theoretically, they could cut short their promises and say that while they promised, say, 3 years of updates - but only delivered two Android updates - that they have fulfilled their promise. Only time will tell.