I have just purchased Production Premium 5.5 upgrade from 5.0 and want to know if my plug-ins will need to be reinstalled or will they automatically transfer into the upgrade?
You will most certainly need to install the plug-ins in the new versions of the software. I would recommend posting in the product specific forums regarding the compatability of the plug-ins with CS5.5 or contact the manufacturer/developer of the plug-ins directly.
will they automatically transfer into the upgrade?
No, they won't, since the apps will be separate installs. The rest is a matter of mybe or maybe not. For After effects, many plug-ins will just work fine, but for Premiere Pro some will definitely need updating...