"Do I think it will happen? Yes. Is it right? I can't see an alternative and it will help our income from the stadium," he told the Echo.
"That will help Dave Jones with the team."
But Ridsdale hinted that Blues supporters may not be happy about the arrangement.
"The council have gifted Cardiff City land for the stadium and we will own that stadium.
"We were asked to talk to Cardiff Blues. The previous owner of this football club (Sam Hammam) said: "Over my dead body".
"But how do you think the rugby supporters feel? Their club is going to be tenants of Cardiff City in a football stadium. How do you think they feel about that?"