SilverWook said:

Having to explain to the audience why Chewie's not around would be awkward and sound forced

I don't know the details of Cheewie's death (I don't even know in which novel they made it) and I don't really care about it. But I have to disagree with what you said. Something like that really doesn't need detailed explaining. All it needs is a scene where Han or someone else mentions it.

For example in ROTS, the kidnapping of the Palpatine was a major plot point that was never directly explained in the film and yet it worked okay. The kidnapping was shown in the less known Clone Wars cartoons.