1) Voldemort & Death Eaters don't like anyone that is half anything.
2) Neville Longbottom is a pureblood. Right? But is 1/2 blood referring to 1/2 royal? or 1/2 muggle? (which is then a mudblood)

What will Year 6 bring?
3) Harry, Ron, and Hermoine will be 16
4) The wizard world is going to war
5) Sibyll Trelawney has made 2 accurate predictions, not just 1. Her second, which happened the night she made the prediction (Year 3) and was about Peter Pettigrew (Scabbers):

It will happen tonight. The Dark Lord lies alone and friendless, abandoned by his followers. His servant has been chained these twelve years. Tonight, before midnight... The servant will break free and set out to rejoin his master. The Dark Lord will rise again with his servants aid, greater and more terrible than ever he was. Tonight... before midnight... the servant... will set out... to rejoin... his master...

JKR didn't hide much in that one. It was pretty much just as she said. Scabbers "broke free" from Ron, turned back into his human body and then ran off to find Voldermort.

6) Neville and Harry were both born in July (seventh month).
7) Both sets of parents fought Voldemort. How many times? All 4 were in the Order of Phoenix.