During a stream today, Marvelous revealed that Rune Factory 5, which was revealed during the Nintendo Direct earlier this year, will have save data bonuses if you have save data from Rune Factory 4 Special, which comes out later this year.
Regarding what sort of bonus it will be, Marvelous only mentioned that it will be “a really good thing”. No further details were given.
Near the end it was teased for Rune Factory 4 Special that there might be a possibility of Ventuswill becoming a marriage candidate (Ventuswill has a human form not seen normally in the story), though not confirmed.
More info is to be revealed in the future.
Rune Factory 4 Special releases for Nintendo Switch in Japan on July 25, 2019. It’ll come Westward later in 2019. Rune Factory 5 is in development for Nintendo Switch.