This question got me thinking: If Iblis has free will, as all jinn do, it would stand to reason that he is capable of realizing the errors of his ways and praying to Allah, regardless of whether Allah would accept him back. However, I have never seen or heard anything suggesting that Iblis is capable of calming his pride and anger. Does Iblis have the capacity to change? In 7:14-15, Iblis requests reprieve and is granted it. Even if Allah has no intention of taking Iblis back, is it possible that he is left to his own actions in order to give him time to see the error of his ways?
Allah (swt) is The merciful.
Iblis asked Musa (pbuh) that can you ask Allah (swt) if there is forgiveness for him. Allah (swt) said yes if Iblis does the prostration to Adam (pbuh) at Adam's (pbuh) grave.
When Musa informed this to Iblis. Iblis became very angry and said did not prostrate to Adam (pbuh) when He was alive, do you think I will do that now that He is dead.
So the door of forgiveness is open for Iblis but Iblis chooses to be arrogant.
First let me correct you by saying that Iblis/Devils <> Jinn. Shaitan is a Jinn but a Jinn is not necessary Shitan. Shitan is a given name to those Jinn who disbelieve in Allah.
To answer your question, Iblis was an Jinn Angle (many scholars would differ but it is clearly stated in the Quran) that refused to obey Allah's order because of his Pride and was thrown out of Heaven. Iblis's pride is so deep that he asked Allah to give him time till the end of Judgment to lead astray that kind that he was asked to prostrate to.
Allah can do anything, he can even erase us all from memory after the day of Judgment so he choose to. However, we believe that he promised us Heaven and promised Iblis and his followers hell.