What's up with the ending? Nothing, actually. There's nothing up about this ending at all. It's a big ol' bummer, and we'll tell you why.
But first, let's revisit. Jody's Grandfather has just told his grandkid that "Westering has died out of the people […] It is finished" (4.163).
Now, this is bad news for Jody, who dreams of adventures like the ones his Grandfather had when he was the leader of a wagon train headed for California. Basically, old Gramps is telling the kid, you know your dreams? Yeah, ain't gonna happen.
So what does Jody go and do? He makes Grandfather a drink:
Jody ran into the kitchen where his mother was wiping the last of the breakfast dishes. "Can I have a lemon to make a lemonade for Grandfather?"
His mother mimicked—"And another lemon to make a lemonade for you."
"No ma'am. I don't want one."
"Jody! You're sick!" Then she stopped suddenly. "Take a lemon out of the cooler," she said softly. "Here, I'll reach the squeezer down to you." (4.166-169)
The poor kid is just trying to do a nice thing for his Granddad, and his mom thinks he's sick? Yeah, that struck us as odd, too. But it's clear that Ruth Tiflin knows her son well, or at least she thinks she does. And it's out of character for her son to be making lemonade for another person, and not one for himself.
That's why she stops. She realizes something—her Jody isn't the same Jody anymore. Something has changed in him. He's growing older, and maybe even kinder. But she knows he's not quite that old—yet. He's still too much of a kid to reach the squeezer all by himself.
Let's back up a minute, for one last thing.
Remember Grandfather's words to Jody? We'll refresh you: "It is finished" (4.163).
Sound familiar? It should. These are the words Jesus said just before he died in The Gospel of John, 19:30. Now, we're not saying that we're meant to think of Grandfather as a Christ figure, but it's worth noting that when Jesus says this in the Bible, it's when he's receiving a refreshing drink of wine. And here, Jody gets Grandfather a lemonade. Hmmm. Seems similar, don't you think? We'll let you decide what to make of it.