I ride to Mandello every year and there is nothing wrong with my sight.
Whilst Guzzi no longer make their own castings, they do assemble bikes at Mandello and there is nothing wrong with the buildings in which this takes place. The empty, badly maintained buildings are no longer used - except for storage.
What they need to make motorcycles already exists at the Mandello site - with room for expansion.
But this is not the problem - the fundamental issue is that they are not selling enough bikes - perhaps not enough to be viable in the eyes of Piaggio who have Vespas, MP3's etc flying out the showrooms of the world. Under the Piaggio umberella, Derby, Gilera, Vespa have the small engines covered whilst Aprillia have the sports range. That leaves cruisers... .
My concern is that it will be Mandello or nothing.
But perhaps you are right and everything will be shipped to Pontedera from Mandello - to continue assembling motorcycles which are being assembled at Mandello with assembly lines moved from Mandello to Pontedera? The Mandello site may be a prime property development prospect.