This answer is rather after the fact, but hopefully the information about other authors with long gaps makes it worthwhile.
Suzanne Collins's The Ballad of Songbirds and Snakes was published in May 2020. The novel is a prequel to The Hunger Games. It is set 64 years before the events in the latter trilogy. It tells the back story of Coriolanus Snow and a previous District 12 victor of the Hunger Games, Lucy Gray. In an interview with publisher David Levithan that was released on the same day as the book, Collins explains:
Focusing on the 10th Hunger Games also gave me the opportunity to tell Lucy Gray's story. In the first chapter of The Hunger Games, I make reference to a fourth District 12 victor. Katniss doesn't seem to know anything about the person worth mentioning. While her story isn't well-known, Lucy Gray lives on in a significant way through her music, helping to bring down Snow in the trilogy. Imagine his reaction when Katniss starts singing "Deep in the Meadow" to Rue in the arena. Beyond that, Lucy Gray's legacy is that she introduced entertainment to the Hunger Games.
To my knowledge, Collins has not been asked about the reason for the hiatus between the 2013 Year of the Jungle and the 2020 Ballad. However, long gaps between successive works are a fairly common phenomenon. For example, JK Rowling published the first four installments of the Harry Potter series at a fairly rapid clip, releasing one book per year between 1997 and 2000. However, the fourth volume in the series was released three years later, in 2003. Subsequent volumes were released every other year.
A starker example of an author with a long hiatus between publications is Jean Rhys. Her collection of short fiction, The Left Bank and Other Stories, was published in 1927. Her first three novels were published in relatively quick succession: Postures (1928), After Leaving Mr Mackenzie (1931), and Voyage in the Dark (1934). It's worth noting that the time between subsequent publications increased with each work: one year, then two years, then three. A gap of five years followed before her next novel, Good Morning, Midnight (1939). She then published nothing for over 25 years. Her work was entirely forgotten, and she lived a life of poverty and obscurity. The release of her last novel, Wide Sargasso Sea (1966), brought her greater acclaim than any of her previous work.
Some other examples: Junot Diaz's short story collection Drown (1995) was followed a dozen years later by his first novel, The Brief Wondrous Life of Oscar Wao (2007). Marilynne Robinson took 24 years between Housekeeping (1980) and the Pulitzer Prize winner Gilead (2004). George R. R. Martin is also known for taking several years between installments of his A Song of Ice and Fire series.
Finally, Henry Roth's Call It Sleep (1934) was followed an astonishing sixty years later by A Star Shines Over Mount Morris Park (1994), the first volume in a tetralogy called Mercy of a Rude Stream. Fortunately, the subsequent volumes were published in 1995, 1996, and 1998; the last two were posthumous, but Roth had completed work on them before his death. Twelve years later, and fifteen years after Roth's death, An American Type (2010), which included some material that had been excised from the tetralogy, was put into final form and published.
In the grand scheme of things, then, the seven year wait between two Suzanne Collins novels (or even the ten-year gap between novels related to The Hunger Games universe) seems quite trivial. Collins has not announced whether she is working on any subsequent novels, and both her own publication history and that of authors' careers in general makes speculation unwise.
