I wouldn't expect another Nas album for at least a year after LT2. December is typically a dead zone for album releases; very hard to get a release date unless you're a star. There are rumors Rihanna and Adele may be dropping this fall or winter, possibly November/December. Also rumors about new Kendrick in that time period. No way Nas or anyone else of note drops then lol.
I think this LT2 album will be what fans want and satisfy folks for a year. Then hopefully we get the re-worked Nas Album Done album next July or September. That's the dream, at least.
As much as I want two Nas albums in one year, I think he should wait until next year as well. Nasir dropped and after a bad roll out and lots of criticism, Nas still held the Lost Tapes 2 and the New album back. If the Lost Tapes 2 is as good as we all hope, Nas could ride it out and and go into next summer on a big and with a buzz.