After the appearance of Gog and Magog

Narrated Abu Said Al-Khudri: The Prophet Sallallahu Alaihi Wasallam said "The people will continue performing the hajj and 'Umra to the Ka'ba even after the appearance of Gog and Magog." Narrated Shu'ba Radiallahu anhu : The Hour (Day of Judgment) will not be established till the hajj to the Ka'ba is abandoned. 
Sahih Bukhari, Book 26, No.663