Hola Diane

As the students progress in their learning they encounter more and more specific content, contexts and nuances that are new for them but are equally important to master. The difference between using the present or the future here is that the present doesn't express that nuance of "wondering" - yes, it is grammatically correct to say ¿qué pasa? of course, and you find this sort of reaction generally in this sort of situation, but using ¿qué pasará? instead means that the speaker is "wondering what is happening", as opposed to a direct question that is simply asking what is happening? Simply waiting for an answering from someone. 

Tenses aren't only used literally, they also have other uses to express a more specific scenario in the speaker's mind, or to create a specific effect. Another example that comes to my mind is the use of the present to narrate past events. Now, one could argue that what's the point of using the present instead of the more literal past. The argument is the same as explained before, there is a particular effect on this usage and this is bringing the past action to the moment of speaking in order to bring the action to the present time to make it seem more real. Although this is a more limited use of the present that differs from the more general use of the present, learners benefit from this knowledge as they may encounter texts using the historic/narrative present if they read a biography for example, and they can then apply it to their own writing, essays, etc.

This is the reason why we cover lots of content that are not just the generic. 

I hope this clarifies it.

Un saludo cordial

Inma