Murphy and Merlin co-creator Johnny Capps previously told Digital Spy that the series could continue beyond the upcoming fifth run.
"No final decision has been made but there is talk [of series six]," Murphy confirmed to CultBox.
He added: "I don't think [the show's future] will be resolved immediately... You'll have to wait and see on that one!"
Murphy also suggested that Merlin fans will have to be "patient" in waiting for the proposed film version and animated spinoff show.
"There's always been talk about both... but in both cases people will have to be patient - these things take a long time," he explained.
The writer/producer insisted that work on a Merlin cartoon would only begin "when the live-action series ends".
"It's very difficult for our actual international partners if we start doing that too soon, so it's a slow burn," he revealed. "[But] we believe an animated series would always work, so slowly but surely something will come together."
Merlin will return to BBC One for a fifth series later in 2012.