What annoys me the most is this idea that I've seen repeated more than once among recent writers that Clea left Strange. In the Annual, Strange says that she left him because there was nothing more for her to learn from him. That's just not true. The last time we saw Clea in Strange's solo series, she 'left' Strange to return to fight in the Dark Dimension, as she'd done many times before. They were still happily married. Strange even muses afterwards that he wished he could join her in the Dark Dimension to help her.
I think that it is true that there was nothing more that she could learn from him, but this isn't what caused the end of their relationship. When Clea was first introduced, she was ignorant of her actual parentage and magical heritage. She was the daughter of Umar which made her half Faltine (ancient beings composed of magical energy). She had been kept in the dark about her potential abilities as well as her true parentage. She was Strange's lover before she became his student. Over the years he did teach her everything he knew, she overthrew Umar (who was ruling the Dark Dimension in Dormammu's absence) and she became the de facto Sorceress Supreme of the Dark Dimension. She and Strange had become equals, but equals who were so busy defending their respective dimensions that they were often apart. Dormammu returned to the Dark Dimension so she returned there too to lead an insurgency against him. She didn't leave Strange permanently because 'she didn't need him any more'. In the meantime, Strange takes up with Night Nurse (and if Fearless Defenders is to be believed, several other women) back on Earth. When Clea found out about this cheating, she decided to end the relationship. She is acting far more mature about it than he is, certainly.
The Annual left the separation open ended, with Clea ready to walk away but Strange unwilling to let her go. In the future, perhaps another writer and editorial group will come along and decide to start writing Strange as an adult again, and maybe they'll pick up on this relationship and repair it. Clea is one of Marvel's longest running characters. FF debuted in 1961. Spiderman debuted in 1962. The Avengers debuted in 1963 and Dr. Strange made his first appearance that same year. Clea debuted in 1964. She's been Dr. Strange's primary love interest practically since Strange first appeared. Her presence or absence in his life is a defining characteristic for Strange. Dropping her from his stories leaves a hole that needs to be explained. Marvel is doing their level best to reboot all of their core characters to make them fresh and new for a new generation of readers. Right now, they want Strange to be single (and apparently they also want him to be phenomenally juvenile and screwed up to appeal to the anime crowd, I suspect). Those changes don't mean that they should just kick Clea off into limbo again, as they did for the last 10-15 years or so. They could use her as a character on her own, separate from (though connected to) Strange if they want to. Perhaps they will. Perhaps they won't.