Harry Potter was a smash hit about a boy discovering he’s a wizard and going to school in a magical world full of wonder and adventure. Twilight didn’t hit quite that high a note, but the story of a teenage girl who learns her classmate is a vampire and falls in love with him did quite well. The Hunger Games popularized the dystopian genre with a bow wielding teenager stepping up to survive death games, have angsty romances, and fight the power.
As far as I can tell, nothing has quite hit that same kind of high since and it may be awhile until the next truly big wave. But if it were up to you, what would the next big thing be about?
This needs to be higher up. A new smash-hit would need to deal with current day issues a bit more overtly. Give kids a way to understand their world and handle their worries.
I think the SF genre definitely has room for that. But magic and fantasy like Harry Potter has way more ability to be timeless than science fiction, where current technology catches up faster. (Would anything really change if HP was set in the 1800’s? Not much, right?)
And I think the publishing industry has changed a lot, so I’m betting the next hit will be a longer series of novellas rather than 700 pages novel length.