In my opinion, the ending of the short story was predictable. When Sergeant Major Morris gave the monkey's paw to Mr. White, the reader could intuit that something bad was going to happen. Morris pretty much says this:
‘An old fakir put a spell on it. He was a very holy man and he wanted to show that fate ruled people’s lives, and that to interfere with fate only caused deep sadness. He put a spell on it so that three separate men could each have three wishes from it.’
Beware of what you wish; you might get it.
This begs the question of whether Morris was an evil man. If he truly believed in the magical power of the monkey's paw, then why did he not destroy it? Why did he teach Mr. White how to use it? Why did he not warm him more vehemently?
As soon as Morris leaves and Mr. White makes a wish (to pay off the house), the reader knows that something will happen. The story does not disappoint. Herbert, Mr. White's son, dies in an accident at work, and they collect money from his death to pay off their house. When Mrs. White wishes her son to live again, something else happens. There is an erie knock on the door. The Whites believe it is Herbert. This terrifies them. What would a resurrected Herbert look like? Finally, Mr. White presumably wishes everything to go away.
Even though the reader does not know the details, it is clear that something bad will happen. More specifically, the reader knows that fate must not be tampered with. From this perspective, the story is predictable.