2Sa 7:15 But my mercy shall not depart away from him, as I took it from Saul, whom I put away before thee.
As many could argue and debate, I shall not pursue now this matter further, for even I myself am yet well learned in this matter. But if I were to choose now, I would believe that King Saul was not chosen to enter God's Kingdom. If one wishes to debate with merely unbalanced emotions, I would say: Alright, he might have entered, by do not be surprised if he didn't, as I would not be surprised if he did.
Only those who seek after God's Kingdom to the end shall see God's Kingdom. Saul didn't seem to exhibit such desire even at the end of his life. One may argue, of course, everyone wants God's Kingdom, Eternity; Then, it is up to how we see such desire as it should be in sync with our behaviors, how we treat people that are before us and after us, recognizing ourselves as sinners not deserving anything - as the thief on the cross.
For there are two kinds: 1. Those whom God showed mercy to but a moment, 2. Those who are God's elects.
This can only be a lesson for us to seek after God's mercy and not make God our enemy.