Nevertheless, how we present ourselves is inevitably influenced by what other people think of us. The amount of influence differs by situation. Though a programmer might dress in jeans and a T-shirt, he surely combs his hair.
Sure, our perceptions of appropriate dress change by the decade or so. But there's a difference between lowered expectations of what's appropriate (business casual instead of business) and no expectation. I think the later is what you're suggesting, that opinions of us are less influenced by our dress.
The former may be happening; but as others have stated, all fashion is cyclical. The later is, in the absolute sense, impossible. In the relative sense, it may sway, just like fashion, but we will always dress based on what other people will think, even if its to a lesser degree.