Doable! Buuuut rendering hair material itself involves transparency work/material storage/etc. Right now UE4 is “just deferred” with limitations on materials and transparencies. How Epic will go about extending is a big question, because it is by no means a “one solution fits all” problem, and thus at the moment is a big area of research for many.
Whatever their solution is, it will have to consider code readability and complexity, AKA how much of a pain it is to write, understand, and modify. As well as platform cross compatibility (what shader functions does it need? How much bandwidth or whatever does it take up?) and a lot of other things. Getting it “right” for UE4 will be difficult, so I wouldn’t expect it, and thus a fur/hair solution that looks good, to be out for a while, at least from Epic themselves.