Not even the originals would've sold 5 million XD Resident Evil 6 hasn't even sold that and that series is much more popular than Devil May Cry. When you compare it to other series, Devil May Cry isn't as big as other titles like Resident Evil or Metal Gear.
I think the reason why they said the 5 mil thing was them wanting to introduce more people into the series. But poor advertising in the early days wasn't a wise choice. I like DmC, but I still hate that debut trailer and how Dante originally looked in it. Even if there were things cool about it with the fighting, they should've worked more into having Dante look like Dante from the get go, instead of Capcom pushing Ninja Theory so hard into changing his design.
Don't get me wrong, I like the black mohawk and his look, but if a DmC2 happens that's one thing I'd want them to do, make Dante look like a Dante. He's already behaving like one by the end, now he just needs to dress up and get that demon hunting business up and running.