The reason we haven't seen Luke in any of the marketing prior to The Force Awakens? It's not because of some mysterious search to find him, it's due to the fact that he has already died. It's only 30 years later, so we can probably rule out old age (unless he started smoking a few too many death sticks), but the galaxy is a dangerous place, and there's a very good chance that Luke made a lot of enemies, what with the whole bringing down the Empire thing. Basically, the idea is that however it happened, ol' Luke has kicked the bucket sometime between Return Of The Jedi and The Force Awakens. So why is he still a part of the film? He'll either be seen solely in flashback sequences, which will explain what happened to him, or he'll be a Force Ghost who appears to the film's new Jedi. Please, J.J., just no.