Um, no.
First, I HATE Grim-n-Gritty RPGs. I DON'T want to play a game where my PC runs the risk of stepping on a rusty nail and dying. I play D&D to be a hero, to be larger than the common man and to do larger things; not die of dysentery.
Second, I dismiss the notion that D&D needs to be R-rated to be relative. Most of the biggest blockbusters are PG-13. Indiana Jones. Pirates of the Caribbean, LORD OF THE RINGS! These movies didn't have a lot of blood or nudity (none, IIRC) and they invoke some great D&D-like adventures, actions, and characters.
Third, D&D has already picked up a darker sheen this last edition: devil-touched PC race, a class about making pacts with otherworldly entities, paladins no longer LG, points of light, Orcus on the cover of the MM, an overall muddier alignment system, mischievous and abusive fey, no automatically good monsters (metallic dragons, nymphs, unicorns or deva-angels) and a distinct shying away from high-level or high power good guys to keep the world safe. Thats a much darker D&D than 3.5 presented in its core rules...
Lastly, D&D is still marketed to 13-35 year olds; those who got into fantasy via Magic Cards, MMO's, some fantasy novels (Harry Potter, Eragon, etc) and movies like I just mentioned. I think D&D would do well to continue to target that core constituency and focus on the same general violence/sex level as those items.
In short: I don't think D&D needs to become more graphic or gritty; it does perfectly what it does right now.