It's unlikely that the interpretation is jump for joy.
First of all, it would be unidiomatic to say you are going to have to jump for joy. If jump for joy had been intended, the construction of the phrase would more likely have been:
You will jump (for joy) after reading it.
But just you will jump after reading it would have sounded strange.
It's much more likely that jump for it means:
You're going to have to work for it.
A different idiom that actually works with this sentence construction is jump through hoops:
You're going to have to jump through hoops for it.
In other words, they are not just going to give it away—it's not within easy reach. They won't simply say what this new word is; instead, in the article, you're going to have to figure it out yourself from the cartoon that follows.
Note that figuring it out is not at all difficult. The cartoon that follows clearly says it up front. That kind of defeats the build up of saying it requires any work on your part to discover. It would be similar to somebody saying, "I'm thinking of a number but I'm not going to tell you what it is. You're going to have to guess." But, at the same time, holding up a sign that reads "The answer is 42." It's an attempt at humour that doesn't quite work.