Yes, exactly. A successor could theoretically replace Word, but first it needs to replicate all of its existing functionality.

For a competitor to supplant Word, it would need to:

- Be fully backwards compatible with .docx. Lawyers will inevitably receive .docx files from counterparties that they need to review, redline, and mark up. The new processor has to handle everything Word does flawlessly. (As an engineer who has spent considerable time building a high-quality docx comparison engine, I can tell you this is tremendously difficult.)

- If it introduces a new file format, support seamless comparison and conversion between that format and .docx. Not technically impossible, but also tremendously difficult with marginal upside.

- Defeat the Microsoft Office bundle in the market — meaning it either offers enough advantage that organizations pay for both, or it replaces Excel, PowerPoint, and Outlook too.

Given the enormous challenge of building a viable Word competitor and the marginal room for improvement that Microsoft has left on the table, I think it's very unlikely that a competitor will threaten its market position.