Ahhhhhh, that is such a good point, well thought out. God, what a morbid episode that has turned out to be then!
I did predict ages ago that Ted and Robin would get back together after the mother would die (Similar sitcoms like friends and scrubs love to do this shit).
They've squashed the idea of Ted/Robin ending up together so many times that I don't really get why people still think it's going to happen. They set in stone a long time ago that Marshall/Lily and Robin/Barney would end up together and happy, the question was always about what would happen for Ted.
Had a feeling for the last season or two that the outcome would be the mother dying. They've pointed to it a few times now though so it's a question of whether they're trying to bluff us and have a twist come the end (Imagine the comedy of the mother being alive and Ted being the one that dies
). If she dies I expect they'll do the entire 'she died but he ended up happy because he had his kids and despite her dying, he found his true love'...and that can work and not every show has to end on the most happy note possible, but on the other hand...nine seasons, nine entire seasons of this guy trying to find the one and end up happy and you then end the show with her dying, I'm not sure even him still ending up happy with his children can make up for that. God knows, I'm torn on it.