He looked perfectly healthy riding off on that horse. Of course Joey seeing blood may have been the film's way of telegraphing an eventual death. Who knows.

SPOILERS BELOW

Watched this again recently, so maybe can help out. Shane does not appear to die in the film, but he does get shot badly in the final fight scene so it's uncertain if he lasts much longer after riding off. Given it was made in an era of Westerns with one-shot kills, when you're either dead or alive and not much else in between, it is hard to tell.

I also got to read it in high school for English (30 years ago now...bloody hell...) and as I recall the ending in the book was also similar....he rides off wounded badly with the young kid calling out "Come back Shane! Come back!". We were kind of told that the open ending was on purpose.

It made absolutely no sense for Shane to ride off if he wasn't sure he was fatally wounded. He could have got medical attention and settled down as a farmer or been a local vigilante.

At the time I didn't think his life was in danger, but having read this thread and remembering he looked slightly awkward on his horse, I think he was a goner.

Going solely by how played in the film (which I've just finished watching), my read is that Shane is not hopelessly wounded and that he survives.

Fergoose, he states, at the end, that he can't stay as now he has done killing there and needs to move on.