According to MA, the original version of the scene was like that and Sisko was trapped with the Prophets for eternity, but Avery Brooks was uncomfortable with it because he feared some in the audience would see it as a brown man abandoning his pregnant wife. When he explained his concerns to the writers, they rewrote and reshot the scene with Kasidy to include a promise to return some day. Avery Brooks may have been right that a black role model like Sisko shouldn't end the series that way while those stereotypes still exist, so I don't fault him for that, but I prefer a more ambiguous interpretation of the ending.
I love Brooks as much as anybody (Well, as much as anybody should!
) but I hate that line of reasoning. Especially as the most famous similar plotline would be the ending of Close Encounters when the decidedly non-black Richard Dreyfuss ditches his family for aliens.
Still, I don't mind it so much these days. We know that if Sisko does
never return then Jake will ruin his entire life trying to get him back ala The Visitor. Which would negate the point of that episode and Jake's sacrifice in it.