The development of English as a global language has urged the field of Teaching English to Speakers of Other Languages (TESOL) to implement some reforms in relation to textbook design and curriculum development as well as the approaches to and goals of English language teaching (ELT). From the multilingual perspective, Global Englishes (GE) and translanguaging have both challenged the traditional native-oriented goal of ELT. Based on the level of language policy planning in the multilingual Greater Bay Area of China, this paper addresses the need to incorporate GE and translanguaging into textbook design and curriculum development. Referring to Byram's framework of cultural content in textbooks, and to the GE proposal of exposure of multilingualism/multiculturalism and respect of diverse culture and identity in ELT, the paper further reports a case study to analyse the cultural content of the textbook, "Speaking Critically: Intercultural Conversation." The paper also explores university students' attitudes towards the integration of Chinese local culture into textbooks. The paper ends by addressing some challenges associated with translating GE and translanguaging into textbook design and curriculum development, and it provides further implications of such a proposal.