Had this old interview with Nas from the God's Son days and Nas said then, when asked about the Lost Tapes 2, that he had enough for a LT2, 3, 4 and 5. That was over 15 yrs ago. I bet when he talks about LT2,3 and 4 now, he is talking the best of the best. It makes me think that aside from the classic I Am shyt that leaked, Nas only allows some of his lesser work to go onto mixtapes and just get out. He stockpiles the best shyt for projects like these and soundtracks, etc.
Nas gonna put shyt out between, at least every 2 albums.