There’s been speculation on this forum that the series will end with Emma having another child and starting a new chapter in her life. With the uncertainty about contracts and season 7, this new actor could be for a flash-forward to Emma’s “happily ever after”.
I always pictured Emma have a girl, though. One big circle back to the Pilot. And if they want a new person to take up the lead role, making it male seems totally out of left field for A and E. Whether or not this show is actually “strong female” focused, A and E *believe* it is.
So having this guy be a CS kid (who shows up with his daughter) doesn’t quite feel right. But having this be Henry (with his daughter) feels more like OUAT because Henry is already an established character with strong ties to the history and narrative of 6 seasons. In other words, if they are going to hang their hat on a new (non female) character, it’s better to hang it on one who’s already known to the audience.
Also, those two pictures are a bit misleading. The first one, posted by @WickedRegal, does look a bit more Hook-ian. The second, posted by @MatthewPaul, looks more Henry (especially with the plaid shirt and blue coat). But neither is how the writers might envision their new character. And just because he’s played a bad guy in other shows doesn’t mean he is here. That’s just typecasting. Like, Colin isn’t going to spend the rest of his life playing a pirate, for example.