Board Thread:False Info and Speculative Discussion/@comment-25338302-20140910015453/@comment-19765459-20140912001330

Again, it boils down to if Keahu is available to come back. Jeff clearly hasn't got him under contract. So even if Jeff thinks he is going to bring Danny back at some point, whether or not it really happens depends heavily on whether Keahu has gainful employment whenever Jeff gets around to writing him back into the show.

Part of me thinks that they ran into the issue of not wanting to have too many smart people around Scott, because it makes him look more like an idiot. Stiles and Lydia already hold most of the brains in the group. Ethan was originally supposed to be brilliant and devious, but apparently that got dropped because it would have required screen time to show. So clearly two really smart people is the maximum for Scott's personal circle. Everybody else needs to either be irrational (Allison, Cora), green (Isaac, Kira, Malia, Liam...) or only intermittently available (Derek, Aiden, Ethan...). Also notice that Scot's erstwhile "mentor" Deaton (with whom Scott supposedly works with for hours on end) is oddly absent and/or provides little in the way of information.

Stiles, Lydia and Danny would create intellectual critical mass and "True Alpha" Scott would be reduced to being a dog playing fetch (at least one review blog has already dubbed Stiles as Penny from Inspector Gadget, with Scott as Brain the dog).