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.
Almost. Musk uses an ellipsis in his copy in the text that elides some text that is rather detrimental to his claims:
> In furtherance of its purposes, the corporation shall engage in any lawful act of activity for which nonprofit corporations may be organized under the General Corporation Law of Delaware.
And if the argument is "its just boilerplate, the court shouldn't take it seriously", that's an argument I can get behind for something like a EULA - but not for an article incorporating a non-profit whose signatories include incredibly rich and high-profile individuals, who either had their lawyers comb over this contract, or should've done so. "I didn't realize what I was signing" is not a particularly valid excuse coming from Elon Musk.