This kind of thing happens often, where you've got "news", but can't disclose until it's final.

In these situations it can be helpful to use some kind of scale or domain reference.

"We've got some pretty exciting news coming up, and we think it could change the world"

vs

"We've got some pretty exciting news coming up, that should really fire up geologists"

vs

"We've got some pretty exciting news coming up, that gets us closer to understanding the history of Mars"

Set a level of expectation.