Surprisingly many that answers 'no'. Personally I'd keep buying headphones. I think there's something special about them. The closeness, intimacy and the overall feeling I get from them can't really be replaced by speakers.
Once a friend told me that he didn't even want to look at speakers because he's a headphone guy .. that made me realize that I'm not alone, putting a distinction between headphones and speakers. They might serve the same purpose - playing music - but there are differences in how they do it.