Please refer to this answer from MuslimMatters.org:
"Allah subḥānahu wa ta'āla (glorified and exalted be He) had a plan for you before you were born, and He still has a plan for you. Allah’s plan for you is necessary and glorious. His plan is vital to your success and important to the world.
Allah’s plan is not set in stone, as if we were robots pre-programmed in the factory. That would strip us of free will and deny our natures. Rather, I believe that Allah has a flexible plan for each human being: a plan that allows that person to benefit the world with his/her unique talents.
This is in fact the Islamic view of al-Qadar, or predestination. There is no doubt that Allah has decreed everything that happens in the universe from the beginning of time to the end, and that Allah has written it all in al-Lawh al-Mahfooz (the Book of Decrees)."
The believers of every divine religion and the followers of every prophet will enter Jannah (heaven) but not those who know very well about Islam and still reject it.
The Quran says in Surah Ali 'Imran (chapter 3) in verses 113, 114, and 115:
"They are not [all] the same; among the People of the Scripture is a community standing [in obedience], reciting the verses of Allah during periods of the night and prostrating [in prayer].
They believe in Allah and the Last Day, and they enjoin what is right and forbid what is wrong and hasten to good deeds. And those are among the righteous.
And whatever good they do - never will it be removed from them. And Allah is Knowing of the righteous."
Therefore, not only Muslims will enter Jannah (heaven).