Lost Tapes 1 cost nothing to make, no promo and was a success.
No reason why he can't put out another volume from the same era. No reason why he can't put out another 5 volumes, but that's probably being greedy.
The Def Jam era stuff can stay locked away.
There is a good thread on why Nas will more than likely never go back to his Sony material on the Reddit Nas page.