While it's already been hinted at, How I Met Your Mother executive producer Craig Thomas recently confirmed the two major focal points for the upcoming fifth season. According to the creator, Barney and Robin's potential relationship will be one of them.
Thomas says, "Barney's feelings for Robin are out there, and it seems like Robin might have feelings for Barney herself. And it's so much fun to write for two people who are emotionally illiterate like the two of them are."
Oh and the other major focal point? That whole Ted meeting the mother thing. Yeah, she's going to be one of his students this season.