M. A. K. Halliday passed away this past week, April 15th, 2018.
There’s an excellent obituary on the front page of the Australian Systemic Functional Linguistics Association Website, as well as at the University of Sidney: Obituary for Michael Halliday.
In the New Testament world, Stanley E. Porter and David I. Yoon have written a piece remembering his life and work over at Domain 33: In Memoriam: M.A.K. Halliday.
As I see other obituaries, I’ll include links to them below: