If they are going to spend eternity in heavenly bliss then there is no possibility of sin. Man will no longer be able to sin.
man will inhabit a restored, perfected environment
Restored? The original created environment was primed for sin with the introduction of the tree and the serpent. No tree and no serpent and no chance for sin. Obviously the plan was to introduce sin with divine foreknowledge.
Clearly, then, the eternal heavenly bliss can not be a "restored" environment. That's why I asked why not just make a perfect world to begin with and spare everyone all the blood and guts and anguish?
“If they are going to spend eternity in heavenly bliss then there is no possibility of sin. Man will no longer be able to sin.”
I guess the answer or the question is, “What is man’s highest good?”
I suppose that if ones happiness involves the ability to sin, to “act not in accord with reason informed by the Divine law”, (St. Thomas, “De malo”, 7:3), then heaven in the presence of “the One who alone is essentially and perfectly good “would probably be hell and one would not want to be there with Him. The ability to sin carries with it the tension, the anxiety of offense; but there will be none of that in heaven.
Back to Augustine, “Man’s original capacities included both the power not to sin and the power to sin ( posse non peccare et posse peccare ). In Adam’s original sin, man lost the posse non peccare (the power not to sin) and retained the posse peccare (the power to sin)—which he continues to exercise. In the fulfillment of grace, man will have the posse peccare taken away and receive the highest of all, the power not to be able to sin, non posse peccare . On Correction and Grace XXXIII.