I could easily see Emma becoming more powerful as a result of Rumpel bringing magic into the world. Which is partially why I believe he brought it into this world for Emma, Snow and Charming to use against Regina in the “final battle.” People tend to forget about the “final battle” part of the equation.
But I’m not too sure about August though. I think he’ll just have to sit and wait until the magic takes effect and he can return to being a man.
I’ve also been questioning Rumpel’s true intentions for bringing magic into the world. He could have used dark magic (something he’s more familiar with) but he chose to use true love. And top of that, it’s magic made from the true love of Emma’s parents. I can’t help but think that he did this to help Emma fight againt Regina in the final battle.