I simply don't beelive claims like thes e without a source link. I've heard too many wide claims like this in the past to beleive this.
On mounts (meaning riding horses, not just horses in general):
"Something we’re messing with, and we don’t know where it’s going to end up. There were things with the Oblivion horses. We liked having them. They weren’t the greatest implementation of horses. And now you see things come out like Red Dead. There are more horses in games, and we feel like just the basic implementation we did in Oblivion isn’t going to be good enough. We are currently attempting things with that, and I don’t know where it’s going to end up.” - Todd Howard, Q&A podcast.
Horse can be seen in the trailer about halfway through by the windmill.
Carriages also confirmed to be in the current build.