After analyzing Quranic verses, one can conclude that paradise is a definite vow of Allah (swt) and the reward of the pious believers who completely obey the prophet (pbuh).  One who possesses these traits will truly reach salvation.

One of the prophet’s commands that must be obeyed, is that we have obey “those vested with authority”, know them and fulfill our responsibilities towards them.  Without a doubt, those who don’t obey Allah (swt), the prophet (pbuh) and the Ahlul-Bayt in their words, in their hearts and in their actions aren't true believers and will not be endowed with the blessing of going to paradise, because the Quran says:

“ان الذین آمنوا و عملوا الصالحات لهم جنات تجری من تحتها الانهار”[i].  In reality, heaven and hell are both manifestations of our own beliefs and actions in this world.  As the Quran says:

“ان احسنتم احسنتم لانفسکم و ان أساتم فلها” If you do anything good, you have done yourself good, and if you do anything bad, you have worked against yourself”.

Completely obeying the imams (as) doesn’t just mean to claim that one loves them and this isn't something that only the Shia say.  It starts from knowing them and what our responsibilities are towards them, why we even need the imams, etc.

Now if by any chance some don’t believe in the imams, if their ignorance is out of negligence despite them being aware of the truth, they will surely not make it to heaven, but if they have tried to find the truth and strived in this way, but haven’t reached it, they will not deserve to go to hell, because hell is a place for the sinners and negligent, and clearly, those who have seriously tried and yet failed don’t fall under that category.