I had a question like so we all know ibless will go to hell but we also know if you believe in Allah swt you will go to heaven after finishing his sins. Like ya he was given a very long life and he must have deed innumerable but if he believed don't you think he will come to heaven at the end? He himself said he still believes and fear him in Surah Al Anfal verse 48 (8:48) in which he says 'Surely I am quit of you for I behold that which you do not. Indeed I fear Allah, and Allah is stern in punishment.'so like won't he be in heaven after he finish his sentence?
to give a short answer to your question, the answer is NO.
to fully understand the quran we must look at the tafsir. the verse which you have mentioned [8:48], is regarding what iblis said when an army of believers and an army of disbelievers met on the battle field. iblis saw what humans could not see, he saw jibreel (A.S) on the battle field with the believers and he was scared that he would be captured by jibreel (A.S) and shown to the disbelievers. if that happened the disbelievers would not obey him.
[refference : Tafsir Ibn 'Abbas and Tafsir al-Jalalayn]
and now to clarify a little more on the question about iblis forgiven and going to heaven, this following video has it explained very well.
may Allah grant you mercy and guide you to the straight path.
Allah knows best.