Rage gives +4 to Str and Con. When the rage ends, the bonuses end, and the barbarian is fatigued; hence the subsequent penalties to Str and Dex.
After a rage, Con drops from X+4 to X, where X is the barbarian's natural Con score. The situation that Klorox was envisioning is if the barbarian has been so injured that the difference between living and dying is less than the number of bonus HP (2/level) gained through the Con bonus. It has never come up for me.
I would recommend obtaining some healing instead of play-testing this theory.
