Here is my theory on what's gonna happen and what has happened.
neville is the chosen one
Dumbledore knows and has been protecting neville by allowing LV to believe that is his mortal enemy
neville knows as he pleads with Harry not to hand over the prophesy.
Dumbledore was at the Potters death and gave Harry his scar to both protect Harry and fool LV that Harry has been marked as per prophesy.
re gleam in Dumbledores eye theory in Gob. This is because Dumbledore realises that LV has failed to make himself immortal because he has taken the blood from the wrong boy.
this tale will end with Neville killing LV (note-Nevilles increasing powers). Dumbledore reveals all to Harry of how he, Lily and James protected Neville by keeping LV's focos on the stronger boy.
sorry if I ruined it for you, I ruined it for myself