Yes, an interesting question. Will it end decades from now with the Hogwart's head master - the elderly Harry Potter - reminiscing about his glory days?
I am so excited for the last book, yet dreading it because it is supposed to be the last book. I am very conflicted!
You have a point though, I can't imagine Harry being able to kill Voldemort and destroy all the horcruxes in one year. Heck, if Snape was working with Dumbledore when he killed him, it will take longer than a year for Snape to convince Harry he is on the side of the Order. I think one way would be to go into the pensieve with Harry and show him the memory. He would have to stupify Harry and throw him into the pensieve for that to happen.