You're right that a number of the original 4/3 lenses are often regarded among the best of their type for any system. However, they are bigger, heavier, and focus slower on m4/3 bodies with the exception of the Olympus E-M1 which focuses as fast as the older 4/3 bodies with 4/3 lenses.
With the exception of some longer pro zooms and pro telephotos, pretty much any lens type available for 4/3 is now available in native m4/3 lens mount. These native m4/3 lenses are generally just as good or better than the original 4/3 lenses, are smaller, and focus faster. Furthermore, 4/3 lenses aren't stabilised as they rely on in body stabilisation on Olympus cameras. Your Panasonic body is less suited to these 4/3 tele/zooms for this reason.
Panasonic and Olympus have lenses in development which will plug the gap of some 4/3 pro zooms/telephotos, so unless you already have 4/3 lenses, or a 4/3 body you really want to use, I don't see much point in buying the older 4/3 lenses anymore.