What is the difference between the next sentences?
- I will leave in 10 minutes.
I assume it means: I will leave within 10 min.
- I am leaving in 10 minutes.
I assume it means: I decided to leave after 10 min.
The Cambridge Dictionary provides the following explanation:
Future: present continuous to talk about the future (I’m working tomorrow)
The present continuous can refer to the future. It shows that we have already decided something and usually that we have already made a plan or arrangements:
[talking about plans for a tour by a rock music group]
The band is visiting Denmark next May.
I am taking the train to Paris tomorrow.
Warning: We don’t use the present continuous when we predict something. Instead, we use going to or will:
It’s going to rain again soon.
It’s raining again soon.
Represents a near future:
I am leaving in 10 minutes.
Represents something that you're not sure:
I will leave in 10 minutes.
Represents something that you're pretty sure that you will do, you made a plan.
I am going to leave in 10 minutes.