Based on new official word from Blizzard, the new WotLK profession Inscription will actually be released in a large content patch prior to WotLK. No date for this patch has yet been posted, but there isn't much time, so I'd guess it'll hit the PTR pretty soon.
Here's some detailed info. Keep in mind that this was created pre-release, so things might be different when the patch is actually implemented.
http://www.wotlkwiki.info/index.php/Inscription
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