The ESRB requirements for marketing is undergoing changes.
Basically companies can cut together a trailer which is approved for the general audience, even though the content is from an M-rated movie/game. If that’s the case, the trailer needs to feature a four-second preface that reads: ”The content of this trailer has been approved for a general audience”. The background would also be green, a bit like the one below:

The same principal will be applied for unreleased games that are expected to receive a Mature rating.
Other improvements are expected to be made regarding the cross-marketing. For instance Game Informer described it like this:
“Other changes include special rules for marketing games together. M-rated games can be marketed alongside lower rated games, if the publisher can prove that the two games appeal to the same audience. For example, Uncharted has historically been a T-rated game, and God of War has typically been an M-rated game. If Sony can prove that Uncharted fans and God of War fans are the same people, the ESRB will approve Sony placing a paper insert advertising God of War in an Uncharted box. This is something that was not allowed in the past.”
News of the changes comes from GiantBomb.com, who received this statement from the ESRB organization.
“This policy addresses cross-marketing of games, not bundling products together. The fundamental goal is to ensure that the cross-promotion of products is appropriately targeted. In doing so we may consider a variety of factors including the nature of the product, audience composition of the media vehicle being used, the intended audience of the game, whether registered users are of a certain age, whether an age-gate is employed, etc.”

- Donate via PayPal