I heard that Peter Jackson is working on content for The Lord Of The Rings HD-DVD box set.
What happened was that before the Warner announcement Microsoft went to WETA/Jackson to try to court them for an HD DVD exclusive deal. Jackson allowed MS to do some test authoring of LOTR to see how it would look on 30GB HD DVD. Basically, MS did all the work. There was never any signed deal or even a hand-shake agreement about where it would lead: it was exploratory (and New Line had nothing to lose by letting MS do the test authoring).
Naturally since all the bonus material on the DVD sets was produced in 1080 HD, it's perfectly viable bonus material ready for any HD delivery when New Line deems the time is right for release.
New Line has been consistently telling insiders on both sides that they have no near-term plans to release LOTR on HD media. The assumption is that they'll wait to release it prior to the Hobbit's theatrical release when HD media has a broader market and they can use the release to increase interest in the theatrical projection.