I could definitely see this name becoming popular. That said, until it actually does, I would not worry about it. I much prefer Emmeline to Emily which (popular or not) I find incredibly dull and uninteresting (no offense to those who like the name or have this as a name). I would stick with Emmeline.
I like the name Emmeline, although Emily will always be my favorite of the two. It feels less frilly, more like someone you can be friends with, while I see Emmeline being snobbier.
My mother had a distant relative in Canada she really liked growing up named Emmeline, pronounced Em-uh-leen. That doesn't seem to be the common pronunciation here, but from my experience, it's more what people are incline to say when they see it on paper. The spelling Emmaline, however, is more likely to be pronounced Em-ah-line.
Just my observation.