Ana because of the symbolism of the chess piece that Hook has to remind him of his daughter. The Red Queen has been known for chess with a chess castle, using chess terms as metaphors, and in the original book was meant to be shaped like an actual chess piece. This show is pretty good at symbolism, so it just makes me wonder if that chess piece has any clues. Besides, Drizella and Lady Tremaine are in the show and Ana's supposed to be making an appearance in the episode "One Little Tear" so explain where she's been. Plus, Lady Tremaine and Wish Realm Hook seem like they've had some sort of history with one another because of their interaction with each other before he became young again.

With Rapunzel, he said she was locked in a tower by a witch, so that practically SCREAMS Rapunzel.

It's more likely Rapunzel.

When he pulled out the chess piece my immediate thought was Ana, simply because I tend to associate all things chess with her, but like three seconds later I was thinking it definitely sounded more like Rapunzel. Although I do think Ana's a possibility -- that last episode was not being subtle in showing there is "something" between Lady Tremaine and Wish Hook, and I don't think his daughter could be Drizella simply because she's very obviously not missing. It's more likely if they end up making this Anastasia not the same as OUATIW's, though, but then I suppose they'd be no significance the to chess piece.

I've also seen someone suggest Jacinda, which would be cool but, like Drizella, she wasn't really missing until recently, so very unlikely.

The likelihood of Anastasia coming back in this show is 1 in a million (because the writers are idiots, and they think the show's audience is comprised of idiots). Which sucks.

^ I'll say, they still seem to think that just because they sporadically told us that Anastasia isn't Cinderella's step-sister because of the episode "The Other Shoe" that we believe them. I mean, come on, they let us believe it since back in late season 3 because of how the Jabberwocky revealed she had a step-sister that a prince chose over her. Who the hell else could it be? It's obvious that they just couldn't get Emma Rigby because of her schedule but instead of just telling us that like smart and mature adults, they decide to act like stupid little brats and tell us that it never was. It's as bad as when they flat out lied that Peter Pan would not be in the show but later was revealed he would be the main big bad in the first half of season 3. How did a show so brilliant and amazing like Once Upon A Time get made by such MORONS?