As they used to say in the issue with the serial killer convention, and I'm paraphrasing here,
[Show spoiler]"Whoa, Dog Soup is a woman!"
Being a DC Comics property, Sandman will have to be produced by Warner Bros., but that doesn't mean that it would necessarily have to air on a Warner net, although the preference would probably be for it to be on The CW. Current Warners shows that air on other nets include: Chuck on NBC; V on ABC; Fringe and Human Target on Fox.
One thing that I have to say about The CW is their tendency to stock their casts with loads of pretty young things, so although The Sandman doesn't really lead one to think that it should have an ensemble cast, expect the Endless to be introduced a lot sooner in a TV series, with maybe Death becoming a series regular, instead of her just being a recurring character.
For the longest time, Kripke's Supernatural was focused on just the Winchester Brothers, but over time, the cast expanded to include Bobby and Castiel, so he would probably be able to talk down the network suits who might be inclined to have The Sandman be an ensemble show.