As I discuss in this question, one of the early movements that was important in the development of Vaishnavism was the ancient Pancharatra movement, whose sacred texts consisted of detailed procedures to worship the sage Narayana, an ancient incarnation of Vishnu who was the son of Yama god of death and twin brother of the sage Nara. (Nara and Narayana were the previous births of Arjuna and Krishna respectively.) Among the oldest Pancharatra texts we have are the Satvata Samhita, Paushkara Samhita, and Jayakhya Samhita.
But there are some Pancharatra texts that are part of other Hindu scriptures. For instance, a Pancharatra text called the Narayaniya is embedded in the Shanti Parva of the Mahabharata, as I discuss in this question. Similarly, there's a Pancharatra text called the Vasudeva Mahatmya in the Skanda Purana, which is the subject of my question. In this excerpt from the Vasudeva Mahatmya, Vishnu tells Brahma about the various incarnations he is planning to take, and here are the last ones he mentions:
By becoming Buddha, I shall delude by the use of fallacious reasoning and deceit the Asuras who adopting Vedic practices will harass the three worlds.
When the Asuras killed by me as Krishna and by Arjuna in the battles, will promote and establish Adharma (unrighteous practices) on the earth, I, sage Narayana, shall be born on the earth from my devotee Dharmadeva in the land of Koshala, as a Brahmana singer of Saman hymns. O Aja (Brahma), establishing the boly Dharma I shall be the protector of sages who will be born as men by the curse of Munis (other sages) as well as Uddhava, O child.
At the end of Kali I shall incarnate as Kalki. Riding a divine horse, I shall kill highly sinful people of Mleccha origin.
I discuss Buddha being an incarnation of Vishnu in my answer here, and I discuss Kalki in my answer here. But my question is, who is the incarnation of Vishnu mentioned between Buddha and Kalki, the "Brahmana singer of Saman hymns" who would be born in Koshala to Dharmadeva? And who are the sages were cursed to be born as ordinary men?
Apparently the Swaminarayan sect believes that this text is a prophecy about their founder Swaminarayan, whom they consider to be an incarnation of Vishnu. They reach this conclusion because Swaminarayan was born a short distance from Ayodhya, capital of Koshala, and his father is sometimes called Dharmadev. I don't want to speculate about whether their claims are correct or not, but let me just ask, have other Hindus come up with any alternative interpretations of this passage?