First off, if you really want to get into the specifics of word use there is no such thing as a "Duel Gun," it is Dueling Gun. And second what would the significance of saying that an already known gun class is "planned" to be using "Duel Guns" when one could just look at the models that are already in game? I will tell you. There is no significance. The only logical explanation would be that translation itself had a typo and instead Yoshi was telling us that there is a plan for "Dual Guns." And wait a minute... that IS what happened.
And Molly... classic of you to result to completely ridiculous accusations that are entirely unrelated to the current topic.