It doesn't look good right now, but hopefully they can get this right.
I looked at the the 'Flex Builder for linux' bug request on bugs.adobe.com and we're up to 348 votes for. Still very little response from the Adobe folks. Tom Chiverton just posted a comment saying that this has created a lot of discussion within Adobe. So if you haven't voted yet, take a moment and help out (http://bugs.adobe.com/jira/browse/FB-19053). He also posted a link to a very interesting article from InsideRIA that was posted yesterday talking about this and related issues of Adobe and it's lack of developer support. Funny we were talking about the slow compile times at the last Atlanta Flex UG meeting :).
The question remains and hopefully Adobe will get this right. Many of the developers they need to get into Flex are LInux/Java people. How do they expect to compete if they completely ignore this critical development community?
source: http://www.codfusion.com/blog/post.cfm/can-adobe-win-the-ria-war