"It's like empires rising and falling and maybe Mercedes are on the wane," Hill said.
Indeed, Red Bull's Daniel Ricciardo won in Shanghai, after Ferrari locked out the front row in qualifying.
Mercedes, on the other hand, have been making fundamental strategy mistakes.
"In our sport it's inevitable that winning races eventually becomes more difficult -- or you stop doing it for a time," Red Bull boss Horner said in China.
"Mercedes has a very fast car and it's amazing that they haven't won any of these races. But in general, our sport is fairly cyclical," he added.
But Mercedes boss Toto Wolff says the German team won't panic.
"I don't know what's going on," Lewis Hamilton said after China. "Since Melbourne we've gone backwards."
Wolff insisted: "We have to stay calm, put our heads together and solve our problems. Like everything else in formula one, it's complex."