In Season 2, in order to discover who was leaking information to Cersei, Tyrion told Pycelle, Baelish, and Varys that Myrcella would be married away to different houses.
Tyrion told Pycelle she would marry into
Tyrion told Varys she would marry into
the Iron Born.
Tyrion told Baelish she shoud would marry into
In the end, Myrcella was to be married into House Martell. And, Pycelle turned out to be the leak.
This had to just be a coincidence, right? Or, did Tyrion suspect something and knew she was going to House Martell?