First, let me say that I'm not going to speculate on what we'll find in Book 7. Anyone who knows me knows that I'm insane about avoiding spoilers — so anyone planning to leave comments, you've been warned!! Nothing about Book 7!!
Okay, so in reading Sorcerer's Stone again, I've noticed a couple of little things that suddenly seem more significant in the light of developments in the most recent couple of books.
First, when Harry and friends are sorted into their houses, we read that "the [sorting] hat took a long time to decide with Neville" . This is interesting given that we've now learned about the close connection between Neville and Harry. The hat also took a long time with Harry, and it considered — *gasp* — putting him in Slytherin. Was it considering the same with Neville? Interesting ...
Second, there's that bit when Harry, Ron, and Hermione have just figured out who Nicolas Flamel is. In the upcoming Quidditch match between Gryffindor and Hufflepuff, it's announced that Snape will referee, which (at the time) seems ominous for Harry, who, we're told, "sometimes had the horrible feeling that Snape could read minds" . Of course, this makes me think of the Occlumency lessons Snape gives to Harry in Order of the Phoenix, and Snape's powerful demonstrations of Legilimency. Harry was right!
[Update:] And there's another example of this, in Chamber of Secrets. When Harry and Ron arrive at Hogwarts in the enchanted car and Snape catches them, he demands an explanation. Before it's revealed that Harry and Ron were spotted by Muggles, we read: "This wasn't the first time Snape had given Harry the impression of being able read minds" .
Nice to see these elements present right at the beginning, isn't it? I'm sure I'll be discovering little things like this for years to come.
 Rowling, J.K. Harry Potter and the Sorcerer's Stone. New York: Scholastic, 1998, p. 120.
 Ibid., p. 221.
 Rowling, J.K. Harry Potter and the Chamber of Secrets. New York: Scholastic, 1999, p. 79.