Gunn had a fan suggest to him that the embryonic Adam Warlock teased in Guardians of the Galaxy Vol. 2 already has the Soul Stone, thus setting up the character to make his grand entrance in the MCU during Infinity War.
James Gunn has debunked a theory involving the Soul Stone, Avengers: Infinity War, and the tease of Adam Warlock during one of the mid-credits scenes for Guardians of the Galaxy Vol. 2.
Despite the tease during Guardians of the Galaxy Vol. 2, Gunn says Warlock isn’t guaranteed for Vol. 3.
The Soul Stone is unaccounted for at the moment, and Infinity War is expected to finally reveal its location.