There will be spoilers for Cataclysm in this post.
The Prophet Velen plays a long game. He thinks ahead and considers not only the past and the present but the future, which befits one who has lived for over 25,000 years and can see into the future (however malleable that future might become). To the Prophet, racial grudges, territorial acquisition, even revenge for injuries done to his people -- none of it matters. Even the great Cataclysm is unimportant. Because Velen has seen that all the battles we've fought are merely harbingers and the greatest conflict in the universe is approaching. And every son and daughter of the Light, no matter how tenuous his or her connection, no matter what forces he or she has chosen to consort with (be they divine, elemental, arcane or even fel), will have to make a choice and pick a side.
The final battle approaches. The world of Azeroth has been chosen. Good versus evil, light against darkness, life opposing death. What side will you choose?