I thought I heard someone at MAX refer to Panini as Flash Catalyst 1.5, but I could be wrong. I know the Flex framework 'Hero' has been referred to as 4.5, but not sure if Flash Builder will use the same numbers.
Flash Catalyst 1.5 and Flash Builder 4.5 are the public names as of now. Release Dates are still not publicly known. Although they are going from .0 to .5, I would consider them both major updates (especially Catalyst)