Will Satan be Forgiven?

Allah made certain promises with respect to those who will enter the Paradise. Allah explicitly promises that once a person is in the Paradise, he will stay there forever. Allah also states that His promise is final. With respect to **some** unbelievers, many times Quran mentions that they will stay in Hell forever. **To my understanding**, even that does not rule out the possibility that they will one day be admitted to the Paradise. To my understanding, they deserve to stay in Hell forever, but Allah may decide to forgive, one day. My question: Is there an ayah or hadith that explicitly states that Allah stated that Satan and some unbelievers will never ever be forgiven no matter what. (Similar to Allah's promise above.) Further, is there an hadith about whether Hell will exist to eternity or not? (Of course, the answer to this question is closely related to the one above.)