DMC4 was awesome as far as Combat systems go. If Nero was too limited for anyones play style, Dante was still there kicking ass as usual, he was incredibly complex and difficult to master in that game.
DMC4 also sold really well didn't it? If the next one doesn't, it definitely wasn't because 4 started some kind of downhill for the series...
EDIT: On topic, Capcom has lost their damn minds.
DD looks good and all but it doesn't seem appealing character or story wise at all yet. Lost Planet was a new idea with a much more interesting reveal, and look how that series turned out...