Dumbledore's instruction before his death were pretty clear: he wanted Harry to find and destroy the Hocruxes. But why would he take the trouble of giving Harry clues and hints about the Deathly Hallows?
Had Dumbledore already foreseen that Harry would break his holly-and-phoenix wand, thus needing a new and stronger wand? How exactly could Dumbledore predict such things?
Or did Dumbledore predict that Voldemort would want to conquer another, stronger wand to defeat Harry's holly-and-phoenix, because Voldemort's wand was useless against Harry's wand (due to the Priori Incantatem effect)? But wouldn't even the Elder wand still be beaten by Harry's wand? Harry's holly-and-phoenix had already absorbed some power and qualities of Voldemort's wand (as explained in the Deathly Hallows ch. KingCross) therefore it would still overpower whatever wand used by Voldemort.