A time would once again come, according to His plan, when the aspect of eating eternal life would be the means by which man would enter an eternal rest with God afterwards. Adam's death was linked to the plan. To see this truth, we must consider the covenant of sacrifice that was given to humanity through the Israelite nation. Salvation is possible since man must die to pay for his transgression, for the soul that sins shall die. This principle allowing the sacrificial death of another to be accepted as the offerer's death as payment for the offerer's sin deals with the complicated dilemma of sin.
Death pays the penalty.
Since the fall from the Garden, death must result as a penalty. However, nobody said that another innocent and sinless one could not be substituted for a person's debt of death. Since death was the result of sin, God took that principle and made a plan of salvation from death. God, Himself, would become a man and die instead of mankind combined. By no other way could man be redeemed from death.