Consider the following:
Sam says to Sarah "We'll go for a walk soon" Does this mean "You and I will go for a walk soon" or is it saying "I will go for a walk soon, and I want you to come"
Tom says to Harry "We'll get the jacket" Does this mean "I will get the jacket" and 'we'll' is used metaphorically since Harry is also involved, or does it mean "You and I will find this jacket"