No where in that does it imply single though. Barney could be cool with not having kids, if in fact they never do.
The more I thought about it the more I though Robin was really a heartless b#%^. Not only turn the guy down when he's finally given into his feelings, heartbreakingly broken up with a girl he really likes, made a huge amount of growth as a person, and agreed that you would do the same, but then show up with your boyfriend, totally blindsiding him in public and in front of all his friends. That's low.
But then I thought about it more and realized Robin is really broken and afraid. She's never been ok with settling down and getting married, and she knows that if she ends up with Barney again that will be the path she is on. It will take a bit more time for her to be ready for that.
I predict that when they finally get togther, they will end up married pretty soon, maybe by the season finale.