From Barney's history we know he wouldn't object to a blended family, so even if it is Kevin's I doubt he'd mind co-parenting with Kevin and Robin if/when Barney and Robin end up together or if Kevin ends up out of the picture totally (somehow he doesn't seem the type to ditch a pregnant woman, but I doubt Kal Penn wants to sign on as a long term minor character either).
It's funny I was watching the episode on syndication last night and someone (Barney?) said Ted wouldn't make a good best man because he wouldn't be good enough to stop Punchy from panicking and backing out of the wedding or doing something else crazy (citing Marshall's hair shaving incident). In the end Ted saw Punchy through and reminded him why he was getting married. Robin then asks Ted to be her 'best man' if she ever gets married and do the same for her. It just seemed so blatantly foreshadowing to what we saw in the season premiere with "The bride needs to see you Ted" that I think it's Robin marrying Barney and that's where everything's headed. Of course with Nora gone now it was pretty obvious too.
Poor Ted...he'll be the only unmarried, childless one in the group. But at least he's going to meet his future wife at the wedding, right? It'd be nice to actually have the next two seasons show THEM dating and a lead up to a wedding for them as well. It seems like the show's wandered from Ted's story for a while so I hope he gets some progress soon.