The show was renewed for two seasons at once; I would assume it would end at that point.
I'm praying that next season ends with the Barney marriage and the season cliffhanger is Ted meeting the Mother, so that the entire final season stars the Mother and how they fall in love.
I am going to be extremely
pissed if they don't introduce her until the final episode. I want to their relationship, how they get together, not just how they meet!