I guess it's debatable. To me, the invisibility cloak was introduced in Book 1, and Tom Riddle's Diary in Book 2. Maybe she knew all along that they were going to be a Deathly Hallow and Horcrux, respectively. Maybe she didn't.
Most of the details in previous books show up at least once more in a later one. I think the only one that doesn't is the Time Turner.
As for Tolkien, he definitely planned the crap out of that. He built an entire history, SEVERAL languages, and cultures, and huge amount of detail that he definitely did not just make up on the spot.
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