All of the 'sort of rumors' about a new DMC have been spread by fans. There's no reason to believe it aside from almost baseless predictions. It basically goes like this- Fan 1: What do you think of the likelihood of a new DMC? Fan 2: Sparse information that suggests a possibility, which could go for nearly any franchise. Boom, you've got a rumor, regardless of whether it has a good reason to exist.
Also, there's a good chance DMC 4: SE hasn't been worked on since Dragon's Dogma's DLC, as we can't be sure Capcom already thought it was a good idea at that point, and everyone needs a bit of a break after a project like that. For all we know, it could've been worked on for a month and Vergil wasn't even completed in the engine when the teaser was released.
To be clear, I'm not saying that I don't want a DMC 5, or that I don't want DMC 4: SE to be an amazing upgrade with plenty of additional content. I'm just saying there's little reason to suppose these things, so to act like we should be angry if DMC 4: SE isn't essentially a remake is unfair to the people working on this project. If you were happy with DMC 3: SE, you should be happy with DMC 4: SE doing just as much to change the game, even if it has slightly more time to be made.
I'm fine with optimism, but it's the threat of hating on Capcom if they don't meet your unrealistic standards that bothers me.