Product Management has mentioned that Customers NOT under NDA can reasonably be told that FB4 is due Early Spring 2010.
The Adobe LiveCycle ES2 Application Modeling plug-in will be updated as part of LCDS and is not included as part of Flash Builderexcept the core pieces that allow non-LCDS development. This release may be a little later than FB4.
The modeling tool itself is not charged for, but LCDS of course is and it isn’t all that usable without LCDS. LCDS does have developer versions for free though.