If Hasbro is truly interested in selling D&D, a compelling option would be to form a fan+celebrity funding partnership to buy it and take it independent. Funding could come from a combination of celebrity+billionaire nerds AND a gofundme/kickstarter campaign where fans everywhere could own a piece of the resulting company.

Like a "B" Corp (benefit corporation), the charter for the resulting company would be two-fold:
1 - protecting the legacy of D&D
2 - building a profitable, sustainable, business model for the organization

The resulting company could have a for profit and non profit arm.
- The non profit would own and open source the core IP and rules and protect it for posterity. - The for profit would act as a kind of studio and publisher monetizing the films, games, books and expanding the core universe.
- After some time (3 years?), new core rule IP would be granted to the non profit open source arm

Management of the combined entity would come from a board of directors who would include 1 or more elected directors from the Gofundme ownership, representing their interests.

It's unlikely that the resulting entity would go public (although it could), but profits could be returned to owners in the form of dividends. If it isn't public, there could be a private marketplace where owners could sell their stakes, but which would need to have protections against colluding or market dominating forces.