I am thinking Garcia, Sevastova, or Barty will have a random breakthrough at some point. All potentially this year. They all have the game and the mentality (despite a few recent slip ups for the three of them), all it will take is the right draw and timing.
Having said that, last year Coco has proven that at the slams and at Fed Cup that she plays best when a lot of people are watching. And like Wozniacki finally winning a slam, i'm sure Svitolina will eventually prove her detractors wrong and break through, probably sooner than later.