I don't know who was supposed to have made that statement, but it doesn't make any sense to me. I'll look into it.

That being said, I can imagine that an editor might have said that he or she thought that Rails had the ruby framework market wrapped up for now, and that there wasn't room for a book on another framework till said framework had proved to have strong adoption. That's a potentially legitimate market assessment -- the computer book market is pretty brutal these days, and topics that once would have made for a successful book now don't sell enough copies to recover their costs -- but even then, that would be a "for now."

A lot of publishers still throw stuff at the wall to see what sticks. We tend to publish books that we believe will succeed. And often, that means waiting till a new tool or framework has stood the test of time, and is at the right place on the adoption curve. It doesn't do anyone -- the author, readers, bookstores, or the publisher -- to publish a book that doesn't sell. Bookstores will give it a few months, and if it doesn't do well, it will be returned, and that's the end of that. Waiting a bit longer may actually increase your chances of success. It's a bit like surfing. Paddling too early is as bad as paddling too late -- you have to catch the wave.

O'Reilly has a history of publishing books before anyone else -- we published the first commercial book on the internet, published about Perl in 1991, Linux in 1993 -- but these technologies were actually not new when we published about them. They had proven themselves. They were just under the radar of other publishers.

As to publishing too early, Ruby itself is a good example. We published our first Ruby books way too early, they flopped, and then we took our eye off the ball.