So far former member Zayn Malik is the only person from the boy band to release his own material.
But Cowell, who put the group together on "The X Factor", has confirmed that the remaining four young men are working on their own material during their current hiatus, reported E! online.
When asked if there are "any more solo projects for the boys", Cowell replied: "Yeah, there will be more, I'm absolutely sure of that."
He went on to praise Liam Payne, Niall Horan, Harry Styles and Louis Tomlinson for their hard work over the past five years and insisted they deserve their break.