When asked about casting the mother, Josh stated that “I don’t think it should be any sort of stunt casting, I think it would be more interesting to have this fresh, exciting face that Ted has never seen before and neither have people who watch the show.”
Josh is still oblivious to knowing the identity of the mother and likes it that way as he stated “It’s kind of better for me not to know. It serves me to be a little more naïve and just play that truthfully".
It is still unknown if the series will continue for one more season. “It just feels like a big question mark,” Alyson Hannigan said. Season 8 will continue to b treated as if it's last season which means casting for the mother might be cast sooner rather than later.