Are we having this conversation?
If so, I am fully aware of what was posted by both of you. The fact remains sentences in two posts contradict each other (Posts 28 and 36).
If A&E could not remain obedient then we do know whether or not they would sin. As someone else pointed out, A and Not-A are mutually exclusive of one another. It's basic logic. Therefore, the following.....
Is incorrect.
- No question remains pertaining to whether or not Adam and Eve would ever sin because..... "neither Adam or Eve could be obedient though they were sinless."
- We can know because.... neither one of them could be obedient!
- If neither Adam or Eve could be obedient, then we do know their will could and would come into conflict with God's will at some point.
We know they would sin because, according to
Post 36, because being created sinless was no guarantee of obedience AND neither Adam or Eve could be obedient though they were sinless. I am not trying to be unduly critical. I am simply pointing out a contradiction.
Part of the problem with this op is that sin has been defined as a conflict between God's will and the human will. That is a good, true, and valid definition BUT it is not the only definition of sin scripture provides. Another part of the problem is that the op couches the problem in sin, when sin is not the only reason Jesus came into this world. Jesus was coming into the world whether or not Adam or Eve, or anyone else ever sinned and correctly grasping the problem to be solved (
the incompleteness of humanity) is critical. Which is why I suggested listing the reasons Jesus came into the world. When we understand all that Jesus does then we understand something very, very, very important:
Sin is irrelevant to God's purpose creating us! 
Yes, Jesus came to undue the works of the devil and he provided a victory over sin we could not provide for ourselves but that is not the only reason he came and God's purpose creating humanity is NOT limited to the problem of sin. That is true whether or not sin serves God's purpose or not (of course sin serves God; God is sovereign over everything!). You were 100% correct to observe Adam and Eve were incomplete. However, any view of sin that makes it
necessary to God is going to lead to a variety of problems, both scripturally and logically.
Does any of that make sense? Would you like me to walk you through the scriptures to prove the above?