There are more Indian than British speakers of English, and it is now possible to find English speakers in just about every country. What does this mean for English? What does this mean for me as a teacher?
The first, and most basic observation is that students should learn about the Englishes they are most likely to encounter. That is, someone doing business in Singapore is likely to need to understand American, British, Australian, Hong Kong, Singaporean, and Malay varieties of English.
How can I possibly expose my students to this variety? And if English is now pluricentric, and I am a Malay English teacher who wants my students to be able to actually use English in their lives, what can I base my curriculum around?
Perhaps this is one area that Task-Based Language Teaching (TBLT) can be particularly helpful. Instead of focusing on abstract language constructs or grammar points, Task-Based Approaches focus on learning language by doing things. So, for example, models of successful interviews (which, in a plurilinguistic place would likely be heterogenous in nature) can be used as input for the task of doing interviews. This sidesteps the need for one model or variety of English to be used (and tested).
TBLT has been criticized as too Western or as being inappropriate to other contexts. Here is an example of the ways TBLT can aid in both localization and globilization (or glocalization if you prefer).