I don't think they would let Rosenberg anywhere near Moira. He can't write female characters with any consistency.
They need a writer who can write a compelling and dynamic story about Moira, Logan, Apocalypse, Magneto, etc...
They also have to write about Nimrod, Homo Novissima, Karima, etc...
It may even include further run ins between Moira and Destiny and Mystique.
It's a big task to take on writing a huge story about Moira's lives.