'shall' and 'will'
Is there any difference at all between these two sentences?
What will we talk about?
What shall we talk about?
Shall and will are modal verbs indicating the future. Different people use them in different ways, and attempts to distinguish them often end up being more prescriptive than descriptive.
For me, there may be a small distinction between your two examples.
may mean that I am asking you for your prediction of what is going to be talked about.
may mean that I am inviting you to suggest a topic of conversation.
Yes, there is a difference.