The Toy Fair poster was a piece of insider information for merchandisers who needed to know when the show is going to be on so they can plan their marketing accordingly. It's not a place for clever-clogs misdirection, unlike the various publicity interviews where Steven Moffat implied more would be happening in 2013. And at this point, all they have time to film in April before Smith goes off to do his movie in May is one 60-minute special. After Smith comes back, it will be extremely difficult to do anything more for 2013 other than a Christmas special without running afoul of post-production deadlines.
Also, if the TV show were planning a full-on multi-Doctor story with classic Doctors in meaningful roles, Big Finish wouldn't have been allowed to do The Light at the End