This article examines the phenomenon of African migration to post-apartheid South Africa from a language-sociological perspective. Although the subject has been one largely neglected by language scholars, the handful of studies which have addressed the issue have yielded ethnographic data and raised questions of considerable significance for the development of theoretical perspectives on the sociolinguistic consequences of geographical and social mobility. In the case of African migrants to South Africa, mobility is often seen to entail a reductive reordering and re-evaluation of their linguistic repertoires which serve to both index and be partly constitutive of their unequal social status. In the final section of the paper, I argue that conventional language-planning approaches, and in particular those which place an emphasis on various forms of language rights, are epistemologically disinclined and therefore ultimately theoretically unable to meaningfully address certain types of language-related problems which may arise as a consequence of mobility. Indeed, it is doubtful whether such problems may be amenable to resolution through any form of planned intervention. Such an insight serves as an important brake on ambition in terms of what can be formulated as realistic expected outcomes of language planning measures aimed at tackling sources of social inequality.