Early last year, MetaFilter had a spirited discussion about SF. Various people were arguing about supposed Progressive bias in the Science Fiction Writers of America (SFWA) and whether an author like Robert Heinlein would even be welcome in SF today. Several people doubted that he could even win a Hugo today.
John Scalzi stepped in to say that not only could he still win, but that he would definitely win today. Scalzi essentially argues that today's SF field is broader than yesterday's. Yes, there are more Progressive voices. But authors are still writing stories in the Heinlein tradition, they still sell well, and they still get nominated for awards.
If we grant that a resurrected Heinlein would read the lay of the land, commerce-wise, could he win a Hugo today? Sure he could -- or at the very least could get nominated. Charlie Stross wrote a homage to late Heinlein called Saturn's Children which was nominated for a Hugo in 2009; its sequel Neptune's Brood is on the ballot this year. Robert J. Sawyer, who writes in a clear, Campbellian style, is a frequent Best Novel nominee, most recently for Wake, which has a clear antecedent in The Moon is a Harsh Mistress. James SA Corey rolled onto the Hugo Novel list in 2012 with Leviathan Wakes, which is solidly in the Golden Age traditon, updated for today's audiences. And I can think of at least one recent Hugo award winner who has a thrice-Hugo-nominated military science fiction series, who has been explicitly compared to Heinlein all through his career. So could Heinlein win a Hugo? Hell yeah, he could -- and if he were as commercially smart today as he was back in the day, it wouldn't even be question of if, but when.