It’s still unclear when Guardians of the Galaxy Vol. 3 will begin shooting, and it doesn’t have an official release date yet.
At one point, the plan was to release Guardians of the Galaxy Vol. 3 in 2020, but due Marvel reversing course with James Gunn months later, The Suicide Squad took priority for him, with principal photography unfolding from September 2019 to February 2020.
Of course, even if the third Guardians movie had kept its 2020 slot, given the current health crisis, you can be sure that it still would have eventually been delayed, just like what’s happened with Black Widow, Eternals and more.