Yeah she's not going to do it for the Hobbit films. She states her reasons why here:
http://www.amagpiesnest.com/shiny_thoug ... f_site.htm Which is a shame but reading her third reason, I don't really think something of this magnitude will be needed for the Hobbit soundtracks. The sheer amount of marketing around the Hobbit films, and all the associated tie-in media that's been released, they will surely release a "Music of the Hobbit films" book fairly quickly, rather than waiting nearly a decade to cash in on that specific fan base like they did with the LotR music. But that's just my personal thoughts.