In an interview with Zap 2 It, creator Craig Thomas discusses the Barney/Robin relationship in great detail,
"We knew we wanted to get to that because they’re great together and we thought we’d get a lot of funny and interesting stuff out of it".
According to the article, the creators saw Barney and Robin as a great team since the first season in Zip, Zip, Zip. We also have some more repercussion between the two of them to look forward to, as well as getting deeper into their relationship. To read the entire article, you can go here.