As mentioned before, a poser is someone who tries to be someone else than themselves. New Dante doesn't try to be original Dante. He IS the original Dante, but in a new interpretation in a parallel world that holds no ties to the original series. They are the same character, but different from one another. New Dante is an individual based on the original Dante, but with his own unique touch to make him appear more appealing to the western gamers.
New Dante can't be a poser, because he is not a real person. He's a fictional character. Just like Megaman.EXE isn't a poser of the original Megaman. They are just two different versions of the same character in two different worlds and game series.
Blade has a long coat, a sword and guns, does that mean Dante is a poser of Blade? No.
Sephiroth has white hair, a long coat and a sword, does that mean Dante is a poser of Sephiroth? No.
Dante from Dante's Inferno is the inspiration for Devil May Cry's Dante's name, but that doesn't mean he is a poser of him.
Someone cosplaying as Dante, is he/she a poser? Well, not unless he/she truly thinks he/she IS Dante, I guess.
The new Devil May Cry (DmC) and the original Devil May Cry (DMC) are in basics the same, but DmC is not a continuation of DMC, rather a new game with a new storyline, not attached to eachother. That means the storyplot in DMC is not the same as the one in DmC, however, there are certain things that are alike. DmC as a start on a new storyplot is then explained as an origin story, not for DMC, but for DmC, to explain how the new storyplot begins.