The potential to be an all-star? Yes. His physical tools are elite. At times he can play suffocating defense and turn that into quick points as we saw against the warriors and other teams during the streak.
Brown also has developed a nice 3 point stroke, hovering around 40% this season. Does he need to improve FT shooting, yes, but I feel that's more of a matter of getting into a good routine and maintaining concentration. His shooting stroke looks fundamentally sound. Nothing whacky about it like a Lonzo Ball for instance.
Give it time. I'm expecting 15-18ppg from Brown this season. Next season, he could easily step into the 20+ ppg range and a borderline all-star as he grows into his capabilities and his body. Remember he's still just age 21 this season.
Also note that there are not a lot of dominant players at the SG position in the East, so Brown could easily claim this position in probably his 3rd year in the NBA.