This avataras (descent) of the Lord is estimated to take place 4 lakh years hence. This will be the last avatar and then there will be dehege.
In Bhagavata Purana,it is stated thus “ When the demons (though devoted to the path of Vedas) will destroy the people with citadels of invincible velocity built by Maya, the Lord will assume a garb that will delude their minds and prove most alluring to them and touch them many a heresay. At the close of Kali age, when there will be no more discourses on Sri Hari even in the residence of pious souls, when the Brahmanas, Kshatriyas and Vysyas will turn heretics and sudras will became rulers, when the uttering of Swaha, Swadha and Vasat will be heard no more, when there will be no talk of sacrifice to gods, or offering oblations to manes, the Lord will take the Kalki Avatara (Punisher of Kali).
Sri Chandrashekar Mahaswami of Kanchi mutt, in one of his books title “Daivatin Kural” – 5th Part has stated that at the end of the Kaliyuga when kama alone unite husband and wife, when cheating will take place on a large scale, when wealth alone will be the deciding factor, the Lord will assume the form of Kalki and descend to the earth. This avatara will take place in an unknown villag e called Saligramam in Tirunelveli district on the banks of the river Tamirabarani. He will be born as the son of a Brahmin called Vishnuyagas.