Sloan closed the season in improved form, helping St George Illawarra win late games and kicking a field goal against Parramatta in the final round.
Despite his expected move to Castleford, rumours that he may stay with the Dragons have persisted, particularly since the Tigers parted ways with coach Ryan Carr late in the season.
Carr, a former Dragons assistant and interim head coach, was thought to have played a key role in securing Sloan, Mat Feagai and Damien Cook for 2027.
Sloan can play on the wing or at fullback, and is known for his speed and attacking threat. The Dragons struggled in those areas during 2026, but Scott Drinkwater, Kodi Nikorima and Luke Metcalf are set to reshape their spine next season.
With St George Illawarra nearing its salary-cap limit, some believe Sloan could still develop alongside young forwards and the new attacking spine. Phillip Sami has also signed after a strong campaign with the Gold Coast Titans.
Castleford have said Sloan will join them, and Sloan has pledged to honour his contract. He is due to begin pre-season training with the Tigers next month.