A large part of theoretical physics is getting to grips with the terminology -- not that you should imply that I'm in any way an expert. I think I'd go with the wording "it seems more like a change in the way we understand the speed of light". From that, it implies that, yes, its definition would change, but it's something much bigger!
So yes, this seems like a huge discovery. Pretty much all of our understanding of relativity is based on the fact that c is, well, immutable. Changing the way we understand c means that we'll need to completely change the way we grok the last century of theoretical physics.
So yes, this seems like a huge discovery. Pretty much all of our understanding of relativity is based on the fact that c is, well, immutable. Changing the way we understand c means that we'll need to completely change the way we grok the last century of theoretical physics.