I think the birth rate will go down / is going down in my country in the next few years.
I think the birth rate will go down in my country in the next few years.
My grandfather is going to retire / retiring at the end of the month.
BOTH
You can trust me. I'm not telling / won't tell anyone what you told me.
You can trust me. I won't tell anyone what you told me.
Will / Shall we invite your parents for Sunday lunch?
Shall we invite your parents for Sunday lunch?
Shall / Will I help you with the washing-up?
Shall I help you with the washing-up?
I'm not having / 'm not going to have dinner with my family tonight.
Both
A It's Alice's birthday tomorrow. B Oh, really? I'm making / 'll make a cake.
A It's Alice's birthday tomorrow. B Oh, really? I'll make a cake.
A What are you doing on Sunday? B We're visiting / 'll visit my grandparents.
A What are you doing on Sunday? B We're visiting my grandparents.
Are you going to go / Will you go to Jo's party next weekend?
Are you going to go to Jo's party next weekend?