Why yes, yes they have!
Actually Panasonic made a new unofficial firmware update, that ship with the new GF1 and GH1. It prevents users from using the GH13 hack
We don't know, why the firmware has been updated. It's quite normal to deliver cameras with a corrected firmware, if bugs have been found. There cannot be an official firmware update for each corrected bug. If I buy a new camera, I definitely want a firmware which is as free of bugs as possible and if Panasonic just does their best to accomplish that, I won't say no.