The first quote from Spielberg comes from the latest issue of Entertainment Weekly:
The question was asked if Spielberg thought there would be another Michael Bay Transformers movie to which he said:
I hope so, because I think he made the best of the three with this last one. I certainly can’t imagine anybody other than Michael being equipped to make another Transformers. He’s invented a genre and he’s got the secret formula.
The second quote from Bay comes from his appearance at the opening of Transformers: The Ride at Universal Studios Singapore:
How did I know someone’s going to ask me this question today? We’re talking about it, but there’s nothing right now. I’m going to do a tiny movie first, then we’ll talk about it, if I potentially do it.