Health was improving
Srila Prabhupada received "warning" several times after leaving India. He suffered two heart attacks while crossing the Atlantic on board the Jaladuta, and then had a stroke in 1967 in New York. At that time, he taught his disciples that they should pray for him to stay in the world in order to finish his work. And when they did pray, Prabhupada assured them that by their "sincere and ardent prayers," his health was improving and he would continue to be able to chant and preach with them.
Reference: Prabhupada Appreciation
Author: Satsvarupa Das Goswami