Here is my theroy:
I think that both Harry and the Dark Lord will die. Because I think when the Dark Lord tried to kill Harry and found he couldn't he created Harry as on of his horocruxes(you'll know what a horocruxe is in Book:6). So when Harry tries to kill the Dark Lord Harry will find that in order for the Dark Lord to die Harry must sacrifice himself. I have evidence to back this up because an interview in 'Harry Potter' Mag there was an interview with JKR about Book & and she said there will be no old Harry Potter