I think that we will get the next announcement before Frodo ships. It's no good for the line to have all of the existing pieces shipped without any news of what's next. I thought we would be at that point with the Star Wars line earlier this year, but they managed to get Luke/Yoda and Boba Fett up before Leia shipped, so they were able to avoid any dead time. I think that we will see our next announcement during one of the ***taculars. It's been eight months since the last preorder, and it can't be too much longer before we see the next one. If it's taken longer to produce, that just means it's going to be a really awesome figure. (Fett was worth the wait.) And it might also be a situation where figure #3 has been a little delayed, so #4 has caught up in the production process, and we will get two of them announced fairly close to each other. Only one LOTR PF announcement in 2006 just seems so unlikely...
(And I would also like to see a third Star Wars PF announced this year, while they're at it.)