Even though a custody battle has been hinted at since episode 5 when Archie threatened to testify against Regina, I would have hoped that Emma would be smart enough not to reveal that plan to Regina. During the entire murder investigation, she told Mary Margaret that the thing that gave them one up on Regina was that she didn’t know Emma knew. Why on earth would Emma suddenly change her tactic?
Because that investigation is over. No longer a need for that tactic.
And I had the feeling that when Sydney came to Emma to tell his obvious lie to cover for Regina, right then and there is when Emma became angry and lashed out at Regina.
Now that Regina knows exactly what Emma’s intentions are, it is only going to fuel a battle over Henry which could result in Henry getting hurt emotionally or otherwise. Even though Regina loves Henry, she won’t stop at playing dirty to get what she wants. She would destroy Emma even if doing so were to hurt Henry.
On the contrary. Henry would like nothing better than for Emma to take custody of him. And to see Emma fighting Regina for him. Henry believes Regina is the evil queen and also believes Emma is the savior. That fight is what Henry has been trying to instigate all along.