Crossed was originally just going to be the Ennis book, but they decided to spin it off since it was so successful. It is definitely an Ennis/Burrows creation.
So far, there has only been one other limited series by David Lapham (who I love), but once this one is over, he'll be doing another limited and a one-shot. I don't believe any of them have anything to do with each other beyond being in the same universe.
You might check out the trade of Lapham's when it comes out. It's not as good, IMO, but it's still really nasty and fun.