Srila Prabhupada reveals in the following conversation the qualification of his successor. If there is an acharya succeeding him, he must meet this criteria. Otherwise he is simply a pretender.
Upendra: We may develop at least maybe half of your energy to continuously preach someday?
Prabhupada: Continuously?
Syamasundara: He says that someday he hopes that the devotees, your disciples, may acquire half of the energy that you have for preaching.
Prabhupada: Why not full, or double? You may have doubled.
Upendra: It's inconceivable.
Prabhupada: Just like my Guru Maharaja did not travel all over the world, so I have got double energy than him. So you must triple energy, four times energy than me. Then actually disciple. My Godbrothers are envious because they could not do. They could not do even half of Guru Maharaja's work, and I am doing ten times. So therefore they are envious. So if an ordinary man like me can do ten times, you are Americans -- [laughs] twenty times, then you are successful.
Room Conversation – April 2, 1972, Sydney