We can use 'will be doing' to predict what is happening now.
They'll be deciding who gets the contract at this very moment. I'm very nervous.
She's not in her office. She'll be having lunch in the canteen.
We can use 'will be doing' to ask extremely politely, and with no pressure, about future plans.
Will you be eating with us this evening?
Will you be needing anything else?
Will they be joining us for dinner?