According to Empire (as reported by Alienbot on the TFW2005 boards), in an interview with Bay, he reportedly said, regarding the Dinobots:

"They've never been discussed [for inclusion]. I don't like them. Actually, I hate them."

Well, me Grimlock not like you Bay either.

He could have phrased it less harshly, since with "I hate [the Dinobots]", he's going to create epic amounts of nerdrage from Dinobot fans. I'm also curious as to why he hates the Dinobots.