Blizzard Beach has a refurbishment scheduled from September 8, 2019 through January 4, 2020. The refurbishment is longer than normal and the expectation is that a new slide will be added at some point by manufacturer ProSlide.
November 20, 2019: WDWNT.com posted photos of water slide pieces being staged in the Blizzard Beach parking lot. They speculated that these pieces are replacement pieces and not a new slide.
November 19, 2019: WDWNT.com is reporting that ProSlide has announced a new attraction could be coming to Disney’s Blizzard Beach. Previously ProSlide has manufactured Summit Plummet and Teamboat Springs for Disney.
July 9, 2019: WDWMagic.com is reporting that the Blizzard Beach refurbishment will take place from September 8, 2019 through January 4, 2020. WDWMagic.com user MansionButler84 is reporting that this lengthy refurbishment should result in at least one new slide.