In my personal opinion, yes I think they do. I honestly can't think of anyone Francine would look better with than Arthur and same goes for Arthur. I think they would be the perfect couple, but they're only in 3rd grade so of course, that would never happen :)
LOL! Well, Francine has a secret crush on Arthur but he thinks the idea is so not awesomeness. But I think that when they grow up they probably will be a good couple. And they actually did get married, I think, because in the episode "And Now Let's Talk To Some Kids" it shows him and Francine when they're old in a house together.
That was interesting, wasn't it? I have a feeling they only meant to imply that one was visiting the other in the future, but it's open for interpretation...