Rush scored 28 goals for Wales during his career.
"It is a fantastic time for Welsh football," he said.
"I never anticipated a day when we would have two Welsh sides in the top league and from a club perspective it has been one of the best years ever.
"I know what people are saying about Cardiff going straight back down. It was the same with Swansea.
"But that didn't happen and now they are in Europe, which is terrific.
"Cardiff will be realistic. They will see their main job as staying in the Premier League and they will need to bolster their squad a little bit.