I don't know about 3rd parties and that things, but for what i know, is that convert one VST to AU when you've got source code, it's easy to do a recompile to make it work on a mac (that on simple plugins) like TSE, LePoulin Plugs, etc.
I asked that to the owner of TSE and he said that he was waiting to get a mac and he would be able to do that compile... until then...