By Ramayana ended, I mean to denote the period of time after Valmiki completed writing Ramayana. What happened to sage Valmiki?
Valmiki is still living. He was also present during the conversation between Yudhisthira and Bhishma which is recorded in Anushashana Parva of Mahabharata. For eg. In this chapter of Anushashana Parva, after Lord Krishna finishes reciting Mahadeva Sahasranaama to Yudhisthira and others, among with other sages, Valmiki also comments there as:
Then the illustrious Valmiki, addressing Yudhishthira, said, --Once upon a time, in course of a dialectical disputation, certain ascetics that were possessors of the homa fire denounced me as one guilty of Brahmanicide. As soon as they had denounced me as such, the sin of Brahmanicide, O Bharata, possessed me. I then, for cleansing myself, sought the protection of the sinless Ishana who is irresistible in energy. I become cleansed of all my sins. That dispeller of all sorrows, viz., the destroyer of the triple city of the Asuras, said unto me,-Thy fame shall be great in the world.