Gwen (Angel Coulby) was crowned queen of Camelot in the BBC drama's fourth series finale.
"All the characters will have moved on a lot [when series five starts]," Johnny Capps told SciFiNow. "Gwen... has a very different role than she's had in previous seasons. When we start series five I think everyone will be surprised where all the characters are."
However, co-exec Murphy sought to reassure fans that Arthur's (Bradley James) marriage would not affect his relationship with Merlin (Colin Morgan).
"I don't think it will change the relationship between them," he said. "I hope it will make it a greater dynamic - three often shakes it up and makes it richer, and without it trying to, I think the writing will do that."
Murphy also promised that Morgana (Katie McGrath) will become "a stronger and more committed enemy than ever before".
"The stakes are becoming higher now that Arthur is king and the future of Albion is being created," he explained. "There's more for Merlin to fight for and more for him to protect."
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Watch a clip from the last series of Merlin below: