When the Ottoman Empire entered WWI, what would the effect be for them in the future?
The effect on the Ottoman Empire was that it would be broken up.
When the Ottoman Empire entered WWI, it did so on the side of the Central Powers. This was, of course, the side that lost the war. The Ottoman Empire had been getting weaker in the years before the war, but this was the last straw for it.
The victorious allies broke up the Ottoman Empire. They put many of the empire's former territories under League of Nations mandates. All that was left to the Ottomans was the territory that is now Turkey. The Ottoman Empire fell and was replaced by the Republic of Turkey under the modernizing leader Kemal Ataturk.