I know the Sony Nex isn't everyones cup of tea & its my first interchangeable lens camera so I know nothing else but I'm delighted to find out that Sigma will definitely be making E mount lenses.
http://forums.dpreview.com/news/1102/11020915sigmacsclenses.asp
Its rumoured Tamron, Zeiss & Cosina might be joining too
http://forums.dpreview.com/news/1102/11020915sigmacsclenses.asp
Its rumoured Tamron, Zeiss & Cosina might be joining too