My headcanon says that RH will play a big part in getting her to back down from magic.
My intuition tells me the same thing. I think RH will know better than anybody the heavy cost of magic, since I think the price he paid for using the fairy wand might’ve been losing Marian. Also, as far as Regina getting what she wants, I think she may discover that what she thought she wanted (revenge/power/magic) and what she actually needs (love) are two different things. We saw this hinted at in the sneak peek from 3×3 when Tink tells Regina that what she needs isn’t power but love. That could be where Robin Hood comes into play since I think Tink will use her pixie dust in modern-day NL to lead Regina to RH. The question is whether Regina can accept romantic love for a second time or not.
"That’s how you know you’ve really got a home. When you leave it, there’s this feeling that you can’t shake. You just miss it." Neal Cassidy