I have a 1TB Tivo box and a V6. Just had an engineer out because the Tivo died and he said I was unlucky as he had one 1TB Tivo left on his van otherwise he would have had to replace it with another V6 as the 1TB boxes were being phased out and they were just going to keep the 500GB ones.
If this is definitely the case my Tivo may just go wrong again in a few weeks