basketball-reference has his probability at 2.1% in large part because he has very few All NBA Teams. Tatum is 59.6% which makes him all but a lock as the only person with a better percentage not in the HOF that is eligible is Marion. Tatum is that high because of the All NBA 1st Team's even without him winning any postseason hardware (I mean we all know he was better than Brown, and led the C's in points, assists, and rebounds in both the ECF and Finals, but for some reason Brown won the MVP's in each of those series).
Now Brown might be one of the exceptions because of the postseason awards (rightfully or not, he does have them). The only 2 people in Brown's range in the HOF are Walton and Nelson and Walton was obviously a league MVP but hurt all the time, and Nelson got in as a coach, not a player.
Of active players, Brown is 36th on the list and currently between Beal and Siakam.
The HOF probability is not an exact science but it is pretty accurate. So I'd say no unless he starts piling up the All NBA teams (and he is clearly on pace for at least the 2nd team this year).