George Williams will join the Dolphins next season, replacing five-eighth Kodi Nikorima.
Their first finals campaign ended Friday with a 36-20 preliminary-final loss to the Sydney Roosters at Suncorp Stadium.
Winger Jamayne Isaako, lock Ray Stone and centre Jake Averillo will also depart, for Melbourne, retirement and the Wests Tigers.
Coach Kristian Woolf remained confident: "I don't think we have hit the ceiling yet," he said.
Woolf said the Roosters earned their win, while the Dolphins were below their best and conceded three soft tries.
Co-captain Isaiya Katoa injured an ankle early and could not find his best form.
Two eight-win streaks, separated by two losses, showed the side was building consistency, Woolf said.
He backed debutants Tevita Naufahu, Brian Pouniu, John Fineanganofo and Lewis Symonds to help the team progress.
Co-captain Tom Gilbert said the squad was "definitely motivated" for 2027 and believed the right pre-season could lead to a better season.