Here are some possible scenarios and food for thought regarding book 7:

  1. Snape dies defending Harry and he is then protected all over again
  2. Nagini is an Animagus – haven’t quite figured out who he is yet
  3. Regulus Black is not really dead – maybe he is actually Nagini and Voldemort is punishing him
  4. Aunt Petunia dies protecting Harry and he is then protected all over again
  5. The Dursleys go to Harry for protection
  6. Maybe Sirius isn’t actually dead? What is the deal with the veil?