The twentieth season of Fortnite: Battle Royale is Chapter 3: Season 2, which released on March 20, 2022 and no teasers were been released for the season before it released.
Usually, teasers for an upcoming season will release daily for the last three to four days of the season and will hint at things such as new items and named locations to be added in the next season and will also hint at the theme of the next season. The theme for Chapter 3: Season 2 was a war theme, and because of the Russian invasion of Ukraine in February 2022, it is likely that no teasers have been released as promoting a war season would be a bad idea at the time.
As a result of this, it is unknown if any teasers were made as it is also unknown how long in advance the Fortnite seasons are planned, so it is unknown if any teasers were made for Chapter 3: Season 2 before Ukraine was invaded by Russia.