I just asked wbacon, the Capcom rep, here on GAF about DmC DE on Steam. No comment. It's really disappointing that DmC is suddenly being ignored, after all this time.
It's funny that a lot of people went all conspiratorial when DMC4SE didn't receive a physical version here in the West, about Capcom being anti-DMC/pro-DmC or something. Somehow it seems like the opposite is true. I'm sure there's an actual valid reason, but I'd really like to know what that is.
At this point, I'd just wager that there's two things mainly at work there.
1) Nobody wants to bother hitting up NT (or another porting team) to allocate time, money and resources to porting the DE on Steam. If they didn't do it close to the release of the console ports last year, then yeah, it's just too late at this point.
2) If they really ARE working on a DMC5 or something to that effect, then it stands to reason that they may be just focusing on just the one aspect of the DMC brand going forward. And that would imply DmC doesn't fit into those plans, anymore than the various Mega Man spin-offs do, what with with the "new" Mega Man toon they're planning to start airing in 2017.