"ever unpredictable" is correct and usable in written English.
You can use it to refer to a situation, person, or thing that is continually hard to predict (i.e. you can never be sure what will happen next). For example, "The weather in Austin is ever unpredictable—just yesterday it was sunny and hot, but today it's raining and cold!".
The tempestuous Smith, though ever unpredictable, is now playing a vital sixth man's role.
And Iraq, ever unpredictable, has from time to time taken its oil exports off the market.
Williams, ever unpredictable, gets a quizzical look on his face when the topic is boot camp, his almost mystical preseason ritual.
Guardiola's choice of formation was, as ever, unpredictable, even once his starting XI was announced but was something approaching a 3-2-4-1 3-2-4-1 3-2-4-1 3-2-4-1
I want you to!" Ever unpredictable, Ms. Love chose this occasion — the release date of "Nobody's Daughter" (Mercury), an album she has been working on since 2005 — to be drab and workmanlike.
Tonight the ever unpredictable Michelle Shocked, whose new live gospel album, "To Heaven U Ride" (Mighty Sound), is unfortunately rather predictable, plays with Toshi Reagon, who sings about love and politics with the same sense of independence.
The first round of baseball's ever-unpredictable play-offs is done.
The tattooed, yellow-haired, ever-unpredictable Dennis Rodman is 37; his legs are weakening, even if his ability to shock and entertain is not.
Under the ever-unpredictable Erdoğan, an increasingly authoritarian Turkey might decide to press ahead with plan B in the event of failure.
Though a number of outcomes are possible in the ever-unpredictable Senate, including censure, expulsion or no action at all, a consensus is emerging that Mr. Monserrate will face a vote on his fate by the full Senate by Tuesday.
There were dangers in relaunching in the middle of an ever-unpredictable fashion cycle, I suggested, but Gur was undeterred: "If you are trying to create a house with longevity, you don't care about what's fashionable at the moment," he replied.
