I am going to take a stab at this one. If there are any comprehension or interpretation errors, I concede that they are all mine and welcome constructive discussions of any mishap.
From my understanding, the ostensibly declining invisibility of Whiteness, and the concomitant work of subjectivity and intersubjectivity, according to Tanaka may be used to foster increasing awareness of privilege, but more importantly, shifts the focus of essentialized categories of race to a positionalities that are ever so precarious and transient, a la Foucault. This departure from former discourses of race and racialization to subject positions in flux must be accompanied by a serious scrutiny of power -- how it operates in particular contexts, including those in which White privilege intersects with socioeconomic disadvantage, or when one's racialized identity is subordinated to one's sexual identity. In other words, identity is not lost into the darkness; rather it is fluid, constantly changing, and repositioning, as it is being negotiated.
The notion of the potential invisibility of Whiteness implies that to begin with, it was easy to detect, and consequently, reinforces it as the Center, which Tanaka calls the "timeless, universal" against which everyone else is measured. Because of its incipient invisibility -- Orlando Patterson argued similar sentiments and called for an equalizing tactic that involved the labeling of "Euro-Americans" -- Whiteness tends to be sparingly espoused in practice, especially when intersected with class, as evidenced in Douglas Foley's Learning Capitalist Culture and the book that inspired me to go into anthropology, The Color of Class: Poor Whites and the Paradox by Kirby Moss. As long as Whiteness remains the norm, it will masquerade under the illusion of invisibility, while continuing to operate under the machinations of Power. That some studies show African-Americans' identities are reaffirmed by the rejection of dominant culture and Whiteness attests to its paradoxical (in)visibility. Thus, decentering Whiteness, as Tanaka suggests, entails diverging from previous discussion of "minorities" and instead, emphasizing interculturality, which allows for subject-to-subject interaction among individuals, all of whom tell their own stories.
The post-racial paradigm is meant to make college campuses more amenable to democratic and egalitarian participation. Rather than moving "beyond" race, this paradigm enables all, including students, researchers, and faculty members to acknowledge its layers, complexities, organicism, fluidity, as well as the power structures in which identity is inexorably embedded. This requires a self-reflexivity on the part of the researcher and academic, with which I concur, to locate one's positionality and how it is shaped by and shapes the research produced. As identities have become more complex and multilayered with the advent of "subject position" and the troubling of notions of "individual agency" by poststructuralists, the arduous task of fighting for social justice remains unscathed. My only question for Tanaka is how this postracial paradigm translates to or encapsulates the seed of potential for activism or community organizing -- Asian Pacific Islander causes, such as NAPAWF or Latino youth movements, such as MECHA -- which are predicated on the very premise which Tanaka attempts to dismantle.