Oh god, I've seen that image plenty of times and I didn't even notice Dante had that sword in him. I thought he was just giving the "...What?" reaction to him.
On another note after doing some research on DMC4 I learnt that this was supposed to be Dante's Devil Trigger. But due to budget cuts and Capcom wanting to rush the game out we got a more simplistic design for Dante. Despite DMC4 being rushed I find it funny how it feels more finished than DmC, that game got triple the development time.
Here's Dante's 'supposed to be' Devil trigger, I like Nero's better.