I have read in multiple forums, which talks about Hanumana being rewarded as future Brahma.
Can anyone point out, where exactly it is mentioned that he is going to be future Brahma?
As per Sanatana Dharma there will be continuous creation and destruction. At the beginning of creation the first Kalpa is Padma Kalpa. It is on this day of Brahma that he is created by the Supreme Being. Each Brahma rules for one hundred years - a mind boggling figure in human years. Brahma's day comprises of one Kalpa - 4,320,086,400 human years. His night is equally long. Therefore Brahma will rule for 72,000 kalpas or 311,046,220,800,000 human years. In our Brahma's reign the first paraardha of half is completed and we are in second paraadha or 51st year of His life. At the end of His life, all creation once again merges in the creator as his Padma Simhasan goes back into the Supreme Beings navel. The Supreme Being then sleeps till it is time to once again re-start the creation.
Valmiki Ramayana states that pleased with his devotion and Services, Mahavishnu as Sri Ramachandra blesses Hanuman and promises that he will be the Brahma in the next cycle of creation.
This is the reference.