For Hell it is said as you quoted:
As for those bound for misery, they will be in the Fire, where they will be sighing and gasping, staying there forever, as long as the heavens and the earth will endure, except what your Lord wills. Surely your Lord does what He intends. (11:106-107)
In same Surah, for Heaven it is said right after the above verse:
And as for those destined to joy, they will be in Paradise, staying there forever, as long as the heavens and the earth will endure, except what your Lord wills—a generous giving, without end. (11:108)
So is Hell eternal? Maybe.
Is Heaven eternal? Definitely.
According to Ghamidi Sahab, Hell is considered to be a “threat” of Almighty, He will execute it in whatever way He wants and if He wants, He can make it Eternal or end it. You can’t stop Him, as 11:107 says, He does whatever He intends.
But Heaven is a promise of Almighty, and Allah never fails His promise. So Heaven will stay forever for according to 11:108 it is a “gift without end”, but Hell will stay forever if Allah wants. A hint from the Qur’an that Hell has a chance of ending if Allah wants it.