Luckily most of the people here prefer the modern grim dark approach. It's better this way imo, the time does not stand still, moving backward is not too reasonable either. WH40k has evolved much from the 1st edition style and there must have been a reason for that.
As far as I would care, reflecting the artstyle of 'Space Marine' would be fantastic. It was gritty, but when introducing the orks into such a style, it makes a very funny clash of art when looking at how they operate.
That animation is amazingly fluid and well done. Just not what i hope to see in EC. It reminded me of the Clone Wars CGI show? Space marines are in huge bulky armor, and though its a second skin to them, they probably shouldn't be jumping around like that. In Spacemarine the animations were perfect, you could feel the weight of the characters just by watching them.
I expect things to be about as stylized as in Space Marine. I think they got the tone right in that game...for a game like this. If this were like a single player game, or an off shoot really different style of game I'd say you could play up the stylization a bit for the focus of the game.
40K's art style has always been stylized but with some emphasis in realism in certain spots. I would almost venture to say that the Warhammer visual style is the very definition of a hybrid stylized and realistic art theme. And with the amount of art out there, I think it would be quite amateur of them if the look isn't right. But I do agree that the animations will be much harder. And what has been stated before, the best asset to refer to would be THQ's Space Marine.
I love the cut-scene where they "jump" onto the Ork train. Bass to full and the floor shakes as three 9' tall dudes wearing full armour drops 15m and hits a steel platform. The SM marines also wore the armour "right", it didn't slow them down or restrict movement (well, except for that Codex-quoting twit who got shot in the face and had to remove his helmet... What does the Codex say about using cover in a firefight I wonder...?!). It'd be really bad if they went Hero-scale (Hero-scale being what the mini's are, huge heads, arms and shoulders with small torsos, waists and hips to focus on the most visible aspects of the mini)
Not a realistic rendering, a slightly "comic" style in a dark atmosphere. Rendering of the environment will be very important.
It's certainly refreshing to see something not cartoony and funny wannabe... I prefer gritty, almost gothic look and feel, there's only war after all.