So I don’t think this is a back pedal. There is a big difference between feeling regret and remorse. You can feel guilty about an action but at the same time not regret that it happened. Especially if something good came out of all of that.
When Regina was tied to the tree talking about all that she’s done, the murder, torture, etc, she actually did sound remorseful. She knew that stuff was wrong and she acknowledged that without Henry she would have felt regret for all the destruction she caused. But she doesn’t because without the curse, and the murder, and the torture, Snow doesn’t meet Charming, Emma isn’t born, and Henry doesn’t exist. And she will happily choose her son over anything else in the world. To me that was one of her most self aware moments in the entire series.
People are complaining that she’s ruined her redemption, but I’m lets be honest here. What kind of redemption are you expecting? She was literally Hitler to the enchanted forest. Bat *&^% insane for 15ish years. You don’t just wash that darkness off your soul. Could she perhaps join the good guys and become some sort of anti-hero? Perhaps. Is that what she wants as a character? I really don’t know. Since the curse broke she’d pretty much been focused on getting Henry back. Once they return to Storybrooke and everything settles down (LOL it’s never going to settle down), then perhaps she can go see Archie and figure out who and what she wants to be. But at this moment, she doesn’t care about redemption or her own happy ending. She just wants her son home and safe.
Now in terms of the promo, I think it has to deal more with the towns issues with Regina, and not her choosing evil again, i.e. perhaps the dwarves are not happy that suddenly Regina is on team Charming.