I'm hugely excited for his book on Aliens.
I just think the first two films have already been documented in pretty exhaustive detail, way before Rinzler ever got involved. I get the feeling that, as much as has been said about the making of the third movie, there's definitely more to know, and a seriously in-depth look could be incredibly interesting, especially given that its production was by far the biggest shitshow in the series.
I'd also shit kittens if he went on to complete the series and do Resurrection, because even Lauzirika's excellent documentary doesn't honestly tell you that much about its making.