We've created this Forum Thread with some workarounds and advice to assist you in publishing you ebook.
I published three ebooks in the past month, the first on May 1, another on May 18, and added iBookstore to a previously published title on May 18th. My experience has been that when a ebook distribution status changes to "Processed" the "Available on iBookstore" button appears on the product page.
In the case of these three titles, they all have a status of processed, but the button has not been added to the Lulu product page and the titles are not available for purchase on the iBookstore.
Is there a problem with the iBookstore feed? Are my titles stuck? Are the Apple elves on vacation?
Edit: BTW- I submitted two support cases. I got the success screen with the support case number, but did not receive the automated email response from SalesForce.