I'm strangely pleased and relieved to hear this news.
For Rid's first return to sci-fi in nearly 30 years, I'm really happy that he's freed from the constraints of what an Alien film needs to be. He had that freedom on Alien, and it was great. He had that freedom on Blade Runner, and it was great, too. Sadly, Alien has become a 'brand' and there are too many interests involved with that brand for anything truly original and genius to be made. Now, Ridley (and Giger, hopefully) can go absolutely nuts.
Plus, ask yourself: were you *really* looking forward to finding out that the Space Jockey was a galactic explorer named Hank who created the aliens in a fish tank, like so many Sea Monkeys, and then was pursued for a while by some woman named Elizabeth Shaw? I mean... who cares?