I have mentioned in the past that there hasn't been much interplay between the worlds of L2 writing and world Englishes -- nor, I suppose, has the whole spirit of world Englishes (or sociolinguistics, or really applied linguistics writ large) had much impact on what we on this side of the biz call "L1 composition" -- those people who pal around at NCTE and CCCC. The reasons for this have more to do with traditional disciplinary boundaries than with willful ignorance, I think, but as I've moved toward this "acceptability" thing (that is, looking at the significance of readers' reactions to texts not in terms of how they treat "errors," but how they react to things the deem unacceptable/inappropriate for a variety of possible reasons) in my own study I've been interested to see that others are moving in a similar direction.
Three important scholars to keep an eye on in this regard are Aya Matsuda, Suresh Canagarajah, and Bruce Horner.
Canagarajah should come as no surprise; you could say that his well-known 2006 article "The Place of World Englishes in Composition: Pluralization Continued" has jump-started the movement in this direction, and really he's been writing about this sort of thing off and on since at least his Geopolitics of Academic Writing (2002).
Matsuda has been writing about world Englishes for the last decade, but she's done some work with her husband, who is an L2 writing scholar, on WEs and teaching writing in the last couple of years. I'm hoping to see more from her on this.
Horner is an interesting case. In recent years he's been working closely with Min-Zhan Lu (whose name I should perhaps have mentioned along with his, but she doesn't much of have a website), the originator of the anecdote (the "can able to" incident, all the way back in a 1994 article) that has animated a number of Canagarajah's arguments on the subject, and they published a kind of manifesto last year on what they call a "translingual approach" to teaching writing. There is much to commend in this article, though as a stodgy TESOL/applied linguistics person I find myself not able to identify with some of its more US-centric perspective and subsequent political positions.
I say "US-centric" simply because composition studies is about teaching writing to college students in America, and there's nothing wrong with that. But its politics are also influenced by its being rooted in American higher education (which again is not wrong! I'm a product of that system and I hope to eventually work in it!), and Horner's statement on how he found his way to a more world Englishes-influenced approach to comp is interesting: "I came to this concern through my work on immigrant rights and English-only legislation in Iowa. This has led me to argue against the English monolingualism dominating the teaching and study of writing in U.S. colleges and universities."
Thus, the notion of "English-only" policies, which are pretty uniquely American, often comes up in his work (the little of it I've seen). Of course, the ideology of monolingualism (which does need to be looked into more deeply) is implicated in most contexts, and indeed this is a reason this 'new' approach to teaching writing is really worthwhile -- but many of us outside the US are simply not dealing with the same political questions. Also, this is where I'd throw in my usual caveat -- "we don't all have the same politics, so let's try to make this palatable to the widest amount of people possible" -- if I had more time. What can I say -- I'm the academic progeny of a "vulgar pragmatist."
In any case, what I like about this approach that is emerging is the way it seeks insights from rhetoric and composition studies, TESOL, sociolinguistics/world Englishes, foreign language teaching, and translation, to be applied to the question of teaching writing to diverse groups of students in different contexts. We could all benefit from more of that kind of thing -- or hopefully, students could benefit from it.