I agree with HoM when he said that the complicated issues surrounding the 5th book is part of the reason that Ms. Rowling took so long getting this book out (that and she got married, and had a baby, and produced a few movies). According to rumors, she thought she had finished the book, and then decided it needed to be completely rewritten.
The resurrection of Voldemort causes some serious problems, especially for those who fought against him before (re: Dumbledore, Sirius, Snape), and, of course, the cause of his first downfall and the three subsiquent failed attempts at resurrection, Harry Potter. I'm sure Hogwarts will also be an obvious target, but I'm not sure that Voldemort is ready to take the school in a head on attack. He's got to rebuild his former power and supporters. Maybe he can do that in 3 months, but I doubt it.
Besides, fear of Voldemort was the biggest problem the first time. Everyone was so busy being frightened of "You Know Who" that they didn't do anything to try and stop him. This is one of the greatest themes in Rowling's books. To fear something is to willingly give it power over you. I'm hoping that as Harry Potter grows through this situation (he'll be 15 this year) that he will be able to develop as a leader. Someone who can inspire courage rather than fear. I also think they should keep the school open for this reason. To close it is to admit defeat.
Obviously, Lucius will again be one of Voldemort's chief supporters, but Malfoy seems too much of a coward to be enthusiastic about it, and I wonder if Malfoy might have a change of heart at sometime.
My biggest question is what will the consequence of mixing Harry Potter's blood into his own have on Voldemort? Dumbledore seemed rather pleased about it, or at least hopeful. Any ideas?