Asked for more information about the return of Manu Bennett as Slade Wilson in the upcoming season, TVLine reveals producers are seeking "an Aussie lad to fill the guest-starring role of an 'introverted, moody and naturally athletic' teenager." While those details are certainly sparse, the implication is that viewers will meet one of Slade's sons on the CW drama (the article's URL even contains the words "slade-son").
Based on the limited description, Grant Wilson is the most likely candidate. The eldest of Deathstroke's children in DC Comics continuity, Grant was introduced in 1980 in The New Teen Titans as an assassin named the Ravager, who's hired by H.I.V.E. to kill the fledgling team of heroes. His death while attempting to fulfill that contract is what triggers Deathstroke's vendetta against the Teen Titans. Grant's backstory was changed in both the New 52 and Rebirth continuities, with Slade attempting to revive his son in the recent "Lazarus Contract" storyline.
Grant Wilson has already appeared in The CW's Arrowverse, in the first season of DC's Legends of Tomorrow. The episode titled "Star City 2046" depicted an adult Grant (played by Jamie Andrew Cutler) who had assumed the mantle of Deathstroke and conquered the city, leaving much of it ruined. He was defeated by Oliver Queen, Oliver's son Connor Hawke and the time-traveling Legends.
Returning Thursday, Oct. 12, at 9 p.m. ET/PT on The CW, Arrow stars Stephen Amell, David Ramsey, Emily Bett Rickards, Willa Holland, Manu Bennett, Echo Kellum and Paul Blackthorne.