It would be... vs. it could be
When my doorbell rings and I think it is my friend at the door, what should I say?
It would be my friend at the door.
It could be my friend at the door.
What is the difference between those two versions?
The difference is if you use It would be my friend that means you are expecting him and him only.
If you say It could be my friend it implies that you are expecting your friend but you think it might be someone else as well.
More natural in terms of quite confident expectation is the use of "should":
Star Trek Generations: A Novel - Page 16 Jeanne M. Dillard, Rick Berman, Ronald D. Moore - 1994 - Snippet view - More editions
But Chekov never got the chance to explain things to Scott; a sonic boom, followed almost instantly by another, distracted him. "That should be him now," he said.