This statement is not true.
According to the iQiyi official website, the fourth volume "Three-Body Death: Eternal Life" is the final chapter of the series of novels and there will be no follow-up.
The novel was serialized in "Science Fiction World" magazine from May to December 2006, and was first published as a single volume in January 2008. There is currently no reliable information that can confirm that Liu Cixin published Three-Body Problem 4. Currently, Human Elegy of Three-Body Problem 4 is only one episode of Gao Xiaosong’s program.