Canadian wrestler El Phantasmo appears to be the newest individual that will be joining the Bullet Club.
During night one of the NJPW New Japan Cup, vignette was aired that hid the person throughout most of the clip but near the end there was a glimpse of Phantasmo. You can check out that clip below.
The Bullet Club currently consists of: Jay White (leader), Bad Luck Fale, Chase Owens, El Phantasmo, Gedo, Hikuleo, Jado, Robbie Eagles, Taiji Ishimori, Tama Tonga, Tagna Loa, and Yujiro Takahashi.