I suspect gameplay is harder to engineer than people imagine. You have to factor in the context ... firstly the mobile device is a phone so it is hard to imagine a game so encompassing that you can't interrupt to take a call. Hence activities which take a few minutes or time-killers whilst waiting in queues are more suited. On the other hand, with the general trend into escapism and AR, it is not impossible to see the phone as an entry point into a fantasy world overlapping with reality. The engineering limitation being that of battery life rather than bandwidth. Despite modern mobiles being more powerful than PCs of a decade ago, generating full vision 3D is still GPU intensive and latency issues start to bite. With transmedia, there is a lot of overlap with movies (franchise), gaming, accessories, collectables etc ... so there's still a lot of combinations left to try (see games around GPS hide & seek). Gaming will substitute for travel/tourism/sport to some extent (both compete in the leisure space) but to come up with a category killer, perhaps a new genre is needed which requires a lot of imagineering and perhaps reframing the elements of social "fun".