I was going to put motorola up on the list of options, but I don't really think there is a chance they will be making the next nexus phone. Maybe the one after, but not the upcoming one.
I would like the see one by motorola though, I've never owned a motorola phone and have absolutely no experience with one. But, now that they are owned by google and google has decided that they will be focusing on quality not quantity, I can see good things happening with the partnership in the future.
What I would like to see is Sony to make the next nexus.