It's not rocket science
Part of the hook in the trailer is whether he lives to fight another day. The way he framed his question (do we want to see a movie WITHOUT) infers that we will see him in another one, thus killing the anticipation. You might as well advertize that Rocky lives
You could just as well say that the trailer spoils that he's sick in the first place.
Damn you movie trailer.
Or maybe I haven't seen the trailer at all and only know that this could be the start of a new franchise.
The truth is that people who haven't seen movies shouldn't be overly exposed to every trailer, discussion, and thing about it before release unless they're unfazed by potential spoilers.
I knew about the film's plot before I even saw it, and I did not spoil it for anyone else.
As a matter of fact, my question presupposes neither the survival or death of Rocky Balboa, only whether his absence would hurt subsequent films.
Your reply makes it pretty fucking obvious, however.