The deal may face opposition that causes it to fail:

https://www.cnn.com/2023/12/18/investing/us-steel-nippon-steel-deal/index.html

Will the deal go through to completion?

Resolves according to reputable news reports or official government sources that the acquisition of the deal has successfully concluded and faces no legal opposition (YES), or press releases from either company officially withdrawing from the deal (NO).

The market date will be extended indefinitely until the outcome is decided.

I will not follow strict legalese regarding resolution criteria as there are many loopholes, so this question will foremost try to follow the spirit of the question.

• Update 2024-11-12 (PST): The market will remain open as long as there are legal challenges to any proposed blocking of the deal, including forthcoming or promised legal challenges reported by news sources. (AI summary of creator comment)

• Update 2025-01-01 (PST): - Market close date has been extended by one year. (AI summary of creator comment)

• Update 2025-06-22 (PST) (AI summary of creator comment): The creator has stated their intention to resolve the market to YES, providing a 24-hour window for users to present evidence of any other serious legal challenges before resolution. See the creator's comment for their full reasoning.