Rigo WAS fertile, many years ago, and his semen was used to inseminate Yuska, to produce Ya Kwanza (now living in Jersey). However, there were previous suspicions that he might have been infertile, and he did have a very low sperm count at that stage. I don't know that semen has been collected since for testing.
So there's a change that he is still fertile, but it my be a slim one.
Australia Zoo has no facilities to hold gorillas, and no plans to build them in the short term, but there's a possibility of moving a male to some other zoos.