Yes, Flex Builder now is named Flash Builder and will be the Flash Platform Coder for Actionscript inside the Adobe Creative Suite CS5. Lee Brimelow write in your blog, The Flash Blog:

We at Adobe expected that the renaming of Flex Builder to Flash Builder would cause quite a bit of conversation in the community and indeed it has. After waking up this morning and reading all the reactions on various blogs and on Twitter, I feel like I need to answer some of the questions and concerns people have.

There you can see some answer for these questions:

• Are you planning on phasing out the Flash IDE?
• Isn’t it going to be more confusing when talking with clients about Flex?
• This screws up my resume and will make job interviews confusing won’t it?
• Will Flash Builder still be based on Eclipse?
• What about the Flex SDK?

Link: Flash Builder rebrand FAQ