If there is not an extreme pivot in Firefox's adoption in the next 5 years, I believe it will be a dead browser. One thing I have noticed is that developers have slowly been forgetting or not motivated to work on ensuring Firefox users have same level features. For example, there are browser extensions for chrome that do not exist on Firefox.

These can range from popular extensions to smaller, more specific productivity extensions. As a specific example, there is a Zendesk extension that can help load all links you click load in a single instance rather than having multiple tabs. It uses Zendesk's built in tabbing system for tickets and is very helpful for workflow.

The problem is this is only a chrome extension, and no such thing exists for Firefox. This is one example but there are so many more, and more of those situations are happening over time.

That is a worrying trend. It means that the chrome browser has such a massive market share, that in a lot of cases worrying about Firefox compatibility isn't even a productive concern anymore. This will eventually end in life support compatibility such as developers putting up splash pages or in-page notifications for users to switch to a more compatible browser. I have already seen extremely rare instances of this, but not enough where I would consider it a concern yet, just an asshole move.