A book worm friend of mine told me the pastime, but he cannot remember where he had read it. There is mention of it here. http://www.veda.harekrsna.cz/encyclopedia/avatars.htm but I was hoping for more details, perhaps Veda you know the reference of the pastime.
The ref is there: Visnu Purana 3.3 - 3.4.5. I don't know about details. SB 8.13.15-16 says that Asvatthama is one of the future saptarsis in 8th manvantara.
Yes, Vishnu Purana Book, chapter 3, verse 20 specifically says that Drauni, (the son of Drona) will be the next Vyasa.
The context is that Maitreya Rsi has asked Parashara Muni to explain the divisions of the Vedas in the different ages. Parashara Muni lists the 28 Vyasa's in the 28 Dvapara-yugas so far and names Drauni as the next (29th). Parashara Muni emphasises a point in the beginning of chapter 4 that the 28th Vyasa, Krishna Dvaipayana, is Narayana Himself: "....for who else on earth could have composed the Mahabharata?"(3.4, verse 5)
Translation: Śrīla Vṛndāvana dāsa Ṭhākura has stated in many places the factual truth that in the future, Vyāsadeva will describe Lord Caitanya's pastimes elaborately. (CC Antya 20.87)
bhaviṣye ha pare cāpi drauṇir vyāso bhaviṣyati (Vishnu Purāṇa, Part 3, Chapter 3 Verse 21)
whatever book that my friend had read described Asvatthama hearing Lord Krishna glories from the mouths of parrots and more specific details were given. If he is able to remember I'll share it here.