It seems like Elon could win a suit to the extent that he could get all of his donations back based on the emails soliciting donation for a purpose that was then changed.
But Elon's goal in this suit is clearly to bring back the "Open" in "OpenAI"- share more information about GPT4 and newer models and eliminate the Microsoft exclusive licensing. Whether this would happen based on a suit like this seems like it would come down to an interpretation of the Articles of Incorporation.