The brand split will remain.
Dave Meltzer of the Wrestling Observer reports that FOX doesn't want to cross-promote with NBC Universal and that "the expectation is split crews would remain."
Raw airs on the USA Network, which is owned by NBC Universal. There had been speculation that the brand split would end when SmackDown moves to FOX in October 2019 with the theory that FOX would want the bigger stars on their brand. Meltzer does note, "We are still more than ten months away from launch and anything could end up happening."
With the crews remaining separate, Meltzer speculates that WWE could start adding more house shows to the WWE Network. WWE will air Saturday's Starrcade on the Network as a one-hour special on Sunday night beginning at 8 p.m. ET.
Meltzer previously reported that FOX wants SmackDown to be "less comedy and more sports focused" when the brand moves to the network on October 4, 2019. FOX wants to promote SmackDown during their football telecasts and wants something more "athletically-oriented" to sell to audiences.