in one of the previous episodes - dont remember which exact episode but i think it was in s7e20 trilogy time - we see barney and quinn some years after they met getting in on at barney's house. So if that happened, how is barney marrying robin now? I think there will be another twist here, something like a double wedding or the bride will come through the door behind robin or something. I just still do not believe that robin will be the one to marry barney.