Transformers owner Hasbro is considering filming the fourth and fifth instalments of the series back to back, reports Variety.
Shia LaBeouf will not be returning for the new films.
Jason Statham is rumoured to be under consideration for the lead role, but no offer has been made yet.
Bay had previously said that he would not return for Transformers 4. He will executive produce alongside Spielberg, but has reportedly also expressed an interest in directing the latest sequels.
Transformers: Dark of the Moon earned $1.1 billion (£700 million) at the box office, making it the fourth top-grossing movie of all time.
Watch Digital Spy's interview with Transformers: Dark of the Moon star Rosie Huntington-Whiteley and executive producer/director Michael Bay below: