There have been 1240 work days since the last book in ASOIAF has been released.
This value assumes GRRM takes off all major holidays (NYE/NYD, Xmas Eve/day, Boxing Day, thanksgiving, his own birthday) and takes two weeks vacation per year.
The average length of an entry in the series is 354,000 words.
This means that GRRM could have written a single page (285 words) per day between ADWD release and today's date and have completed the book. If he only worked for 4 hours per day (20hours/wk), that is 72 words per hour, or 1.2 words per minute.
There are no excuses left for him, or Rothfuss for that matter.
He's either simply not sitting down to write, he's paralyzed with anxiety, or he just doesn't give a fuck anymore.