I think proponents of a DMC 5 sequel tend to fool themselves into thinking either sequel is just as likely as the other. Let's analyze some of the perspectives, here.
One clear reason not to continue the original DMC is that the story has become vague and inconsistent. It would be impractical and boring to try to wrap everything up or shoehorn a story in there that feels 'big' enough. All of the major, most powerful villains are dead. DmC, on the other hand, is begging for a sequel and leaves a lot of creative options to explore in every area- characters, plot, weapons, theme, etc.
Another common argument is that DMC 4 made more sales than DmC has in one month, so DMC 5 would presumably make more money. This ignores several facts- one month isn't long enough to compare the sales, videogame sales have declined since 2008, and DMC 5 is not DMC 4. Whatever the reasons for DMC 4's success, there is no guarantee a DMC 5 could reproduce these results. Additionally, splitting up fans from 5 years ago (presumably 7 or 8 by the time a sequel could be released) and the new, critically-acclaimed fans is likely to bring sales down regardless.
And of course, some people think DMC is 'cooler' than DmC. This is largely a matter of taste, but you can't deny that DmC is a very presentable game by any possible objective measurement, as many reviews have described in detail. And remember, the original team members behind the previous DMCs are not involved anymore, so any DMC 5 would be something of a remake, anyway.
All things considered, it seems silly to even consider a DMC 5.
