Well right now I'm kinda in writers block with my poetry, but I've had some new ideas lately. One I thought I had this morning is sort of a prince/pauper thing, God creates two very similar people but they are born into different cultures and circumstances. They go through life and you see their inner struggles. Not sure, it was a random idea. But a story I'm writing is going pretty well. The main character appears to have died, but it's not clear if she has or hasn't. If she does die, there's a lot unresolved, but if she doesn't there's some avenues to go down. Not really writers block I guess, but a few things not complete.
As far as professional writers, like others have said, I think that some have written stories and release them later. That's what I do with a good deal of my poetry, many times when I post them on a site they're months old. And as far as writers getting people to help out with stories and whatnot, I think anime/manga writers do that sometimes, when they have others work with them in studios and stuff. I'm pretty sure they do some artwork and design, I'm a little uncertain if they write as well.