Hi Walter. I think we're talking past each other. You're talking about the ability of new versions of LR to import catalogues from previous versions. I know that Adobe don't enable that on beta versions, presumably because they don't want people to depend on a beta, and then complaining when it dies and corrupts their catalogue in its death throes.
I'm talking about the cost of purchasing the upgrade. When LR4 comes out, is it likely that I'll be able to buy an LR4 Upgrade pack, and apply it to my existing LR2 installation or must I purchase an LR3 upgrade pack too [or possibly skip LR3 and go directly to a fresh installation of LR4 if that's cheaper than two upgrades]