With the name of the device, Google is clearly giving a nod to Dick's novel Do Androids Dream of Electric Sheep? (the book that was adapted for the seminal sci-fi film Blade Runner): "Nexus-6" was the name of the android model in both the book and the movie.
What's unclear is whether the Dick estate actually has a case, despite Dick's daughter Isa Dick Hackett's proclamation: "We feel this is a clear infringement of our intellectual-property rights." As the lawyers gear up to go to town, they'll be looking at questions like whether or not the name implies Mr. Dick's estate is somehow involved with the Nexus One -- which in reality isn't very likely.
On the other hand, it's certainly not unprecedented -- in most recent memory Verizon had to shell out to George Lucas to license the name Droid for its first Android offering. At this point, only time plus lots and lots of lawyers will tell the outcome here. What's your vote: Should Google pony up to Philip K. Dick's heirs for the Nexus One name?