The announcement came in this week's Marvel comics. The name "Hickman" appeared on pages, bearing an identical style and font to the tease from last week. The page doesn't reveal exactly what book he'll be working on, but it does indicate that it's slated for release in July, meaning that solicits for whatever it is should appear around this time next month, if it's not revealed before then.
Although it's not totally clear at this time for what book Hickman will return, the previous tease narrows down the field a lot. That tease reads, "When two aggressive species share the same environment, evolution demands adaptation or dominance." The language used there definitely sounds like something from an X-Men book. However, some believe that it might also refer to the Inhumans or Eternals. It's also entirely possible that this is a tease for an event comic of some sort.
Hickman has helmed a number of high-profile books for Marvel in the past, including Fantastic Four, The Avengers and The New Avengers. He was also responsible for two major events: 2013's Infinity and 2015's Secret Hickman is also known for his creator-owned work at Image Comics. Those titles have included East of West, The Manhattan Projects and The Nightly News.