Leticia, Ariel R produced HAIM's album, so he may be there as their guest. At the very least, they likely introduced him to Taylor. I do hope She'll work with him.
She is not even sure she'll have made another album by the time 2020 rolls around. "I'm not going to put out an album until I've made one that's better than this one and that's going to be really hard," she says.
Oop. Ha 25 is coming upon us. Let the decade-wait for the next record begins.