The thing is, we can't exactly go by history since we've never been as interconnected as we are now. Intercontinental travel could potentially be seen as "just" a huge step up in transportation compared to the past but the internet has fundamentally changed how we communicate. When it comes to technology and science, English is the de facto standard and it's gonna take something pretty huge to disrupt that.

Never in history though has there already been a language this dominant across the world, has there? I look at it this way, two things need to happen for a new language to become dominant -- there needs to be both an impetus and a strong candidate.

I'm not entirely sure what impetus there would be. What we've had so far is everyone else using the language. What would cause that to happen? You'd need a sizable number of people who simultaneously have global influence and don't typically use English. Right now one precludes the other. It's why there isn't a strong candidate either -- the language would need to have widespread use and honestly be the preferred language in some fields globally.

I can think of two possible candidates, but it's still a stretch. Latin is probably the most widely used, but no one uses it conversationally. Japanese goes along with your comment about movies -- the anime industry has been successful on a global level to the point that people prefer to listen to it in Japanese even if they don't understand it.

I think that's the bellwether we need to look for. Whatever the successor language is, it will need to be adopted by people who don't understand it but still prefer it. It faces the challenge of supplanting the dominant language for the entire globe, not just a region of the world.