(a) Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said that the Messenger of Allah (peace and blessings be upon him) led the Isha prayer in the last days of his life. When he had finished the prayer, he stood up and said: "What do you think of this night of yours?" Then he said: "By the end of a hundred years, not one of the people who are on the earth (today) will remain alive."
(b) Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said: People misunderstood this statement of the Messenger of Allah (peace and blessings be upon him), so that they began to take something else from the hadiths that mention a hundred years, namely that the Hour would come after a hundred years, although that was not what he (peace and blessings be upon him) meant. Rather, the point was that none of the people present on this earth today would remain alive. By this he meant the end of that generation, that is, this era would pass away within a hundred years.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2133