Quote from the movie A Beautiful Mind: "But on the night, here you are, making a Hollywood movie..."
There are just a few movie poster, or other movie related promotional material that hold QR Codes.
The Iron Man II movie poster contained a QR Code in the Uni-Beam of the Iron Man suit.
This QR Code was linked to a online promotion.
I haven't found a Iron Man III movie poster containing a QR Code, it seems that the usage of QR Codes in relation with movies is not consistent.
In my opinion each modern movie poster should contain a QR Code linking to the trailer. QR Codes target the mobile phone users, and most modern mobile phone have no problem running these trailers.
With just a bit of enhancement effort the QR Code can be graphically linked to the movie.
Here is my Captain America The Winter Soldier QR Code. Maybe Marvel Studio's is interested :-)