I have poked around a little for this answer, but i dont want to spend all day doing so as Flex / Flash is not my full time job i am not hip to all the proper places to go to find the correct answers.
Today i bumped into adobe labs, where i saw that there is Flash Builder 4 Beta out. I downloaded it and it looks much like Flash Builder 3 which i own.
What i would like to know is 2 things.
#1) what is the difference between Adobe Main site (which does not even show Flash Builder for their products) and this Adobe Labs site which does show it.
#2) what is the differences between Flash Builder and Flex Builder ?
It figures, that as soon as i posed this i found the answer to my questions.
FWIW, here is the answer.
Please feel free to corect me if i am wrong, but the way i read it and interpret it is that Flash Builder 4 will replace Flex Builder.