The answer to my question proved complicated, here are my presentation slides from the IATEFL Conference in Birmingham in April 2016, in which I revisited research into the future of the ELT coursebook that I started in 2010.

In my research I found printed coursebooks continue to be widely used, and the take up of digital alternatives has been slower than I predicted in 2010.

Teachers and students: online outside the classroom, offline inside the classroom.
[Publisher comment]

I also found that the publishing sector is struggling to make money from coursebooks and digital alternatives, as governments cut budgets, consumers expect content for free, and the result has been very challenging for people involved in the sector, particularly authors. There are some interesting developments and initiatives, but important pedagogical issues still need to be resolved.