It can be used:
to describe something which will be in progress at a
certain time in the future:
The dog which is pursuing James will be barking at him very soon.
Now the dog is not barking, it is running. But when he reaches the tree (an
action in the future), the action expressed by bark will start and continue
for some time.
to denote future as a matter of course (future without
intention):
Pilot: We'll be flying at an altitude of 25,000 feet. (The action will occur in the normal course of events.)
Compare:
I'll meet Paul in the afternoon. (An arranged meeting)
I'll be meeting Paul in the afternoon. (The action will occur in the normal course of events.)