This paper explores the extent to which the research insights in two well-defined areas within the field of sociolinguistics, namely, bilingualism/multilingualism and world Englishes, need to be incorporated in the teaching of ESOL and in our teacher training programs. While the former includes notions like speech communities, verbal repertoire, language transfer, codemixing/switching and domains, the latter is concerned with issues like identity and target model norms. The contributions of the above fields are critical particularly now, for no longer are ESL users primarily from the post-colonial communities, nor is English primarily a language to communicate exclusively with the native speaker. This paper introduces some of the relevant sociolinguistic concepts and offers concrete suggestions for incorporating critical research insights from bilingualism/multilingualism and world Englishes, in the hope that it would help prepare teachers for the 21st Century and beyond, whether in ESL-using country like India or any of the inner circle countries.