As I have stated before, when we play D&D, about 60%-70% of the game is roleplaying and about 30-40% of the game is tactical combat. When we are in tactical combat, we often try to RP the gamist parts of the game so that we can stay in character. 4e D&D is not going to change this at all. When we play D&D, it's far more than a boardgame.
Also, I agree with other posters that state that its difficult to find RP rules in any edition of D&D. How you "roleplay" comes out in the many paragraphs that will be dedicated to classes and races and what their roles are in relation to one another -- not class roles in the 4e sense, but roles in the "how do they get along with..." sense.
There's some of this in the PHB, DMG, Complete xxx, ToM, Bo9S, and PHB 2 -- and I imagine that 4e will have some of this too.