@Rose175, I believe if he cancels, he has to leave. So if he cancels tomorrow morning, you get the two nights he spent and the one night he will not spend, but you loose the five others.
You can also make a change to the booking today for whatever lenght you both agree upon. You could accept a reduction of the stay, not a cancellation to two nights and he moves out immediately and you only get two nights. Not in your interest though.
You could agree ipon four nights and he actually spends them.
Or you could just let him struggle on, hoping he looses more time.
Easiest would be to agree upon a duration, you send him a booking alteration and he accepts it. Do that side by side. If you cannot do it , you can also call airbnb together, on speaker and ask them to do it.
The advantage of an alteration is, that your calendar is free for other bookings immediately.
However, a cancellation gives you a boost in ranking, to consolate you.
But if a new guest calls airbnb all by himself and tells stories, you never know, what will happen.
Personally, I would suggest an alteration now, that closes the open file and lets you move on.
On the other side: I would probably suggest a small fee and get an airbed for the other person. If there is enough room.