If you can predict it, I predict you'll call it predictable. In other words, anything that you can see or know before it happens is predictable.
When she got out the fine china early in Act I, you could just tell the stuff would be smashed in Act III. It was all too predictable. Given the facts of their lives, the end of their relationship was predictable: he was married, and so was she, but not to each other. The roots of the word are fun to analyze: pre- means "before," dict means "to say," and able means, well, "able." Put them together, and you'll see that predictable means "able to be said before (it happens)" or, simply, something you know of before it happens.