Good point. I have a similar opinion like you. About that possible war between them.
The question is, what kind of enemy they could have? Another different species? Or just a different clan of them.
I think that your theory is really close to the actual story. Xenomorphs could act like a weapon of massive destruction in the planetary scale, so again it is probably close to the truth.
You aslo write that perhaps David should call for some sort of help or something like that, so the Ship "Covenant" cold be just another expedition that responds on David message.
Another possibility is, that "Covenant" ship is on the way to the engineer planet, because they capture the signal that dr. Shaw leave before she flew away (Prometheus ending).
My first idea was, that I imagine a dr. Shaw helping David put his head back on the body. But since source is saying that dr, Shaw will no longer be in this movie, I don't know what to think?
She died on the way to the planet? I don't think so, it seems that Engineer Spaceship could fly in the speed of light, we see that in the end of Prometheus, this ship uses some sort of "Jump" technology for flight.
I mean, that should give us a reason to think that dr. Shaw could reach engineer planet in relatively short period of time.
Can David kill her? Maybe after she helping him with his head? Or can perhaps she normally died, because she don't have any food or resources?
Covenant ship as a human ship could perhaps fly slower then the engineer ship, that means dr. Shaw can just die by the time before Covenant ship arrives.
Only David as an android can live for a long time. I'm really surprise what they say us about dr. Shaw.
But I have a strong feeling that she is already dead.
Ridley Scott already said, that we will se all the Xenomorphs forms, that we already know.
The egg, facehugger, chestburster and big boy. So I imagine that if there would be the eggs, there should be even the mother, the Queen itself. Source even say, that there is some sort of small squid like monsters, similar to one that we see at the scene from Prometheus, where the engineer is impregnated.
I'm so happy about this movie, I feel that this is gonna be unique, and I almost can't believe that there will be another opportunity to see a classic Aliens, and even more.
Last question I have is, the picture that you use on your comment, is that from you? Did you draw it? because I draw by myself, so tell me please. And again, please excuse me English, I'm from Europe.