The Guardian's book blog asks:
The term "grand master of science fiction" summons up, for me at least, the image of a venerable, white-haired author who was speculating upon mankind's future when the idea of putting a human on the moon was still a pipe dream.
But the appellation is a distinct honour, awarded by the Science Fiction and Fantasy Writers of America to a living author who is announced, towards the end of the year, to be the recipient of the Damon Knight Memorial Grand Master award. ...
As worthy as all the past winners of the Grand Master award undoubtedly are … what of the next generation? Is it feasible to now cast the grand master net wider, perhaps consider those writers born in the 1950s, or the 1960s? Even someone born as relatively recently as the 1970s could now be in their 40s. Who from that crop would be worthy of the honour?
For me that's easy: John Scalzi and Charles Stross. Between them they have 8 Hugo Best Novel nominations in the last 8 years.