Burnwinter - I don't doubt he certainly wanted to develop him on the wing at least. But if he had planned to eventually move him through the middle, there are a few things that could have held up that transition:-
1) van Persie
2) rubbish alternatives as wide forwards
3) him not developing as expected in certain areas
I'm just speculating really, I have no idea what Wenger intends to do with Theo, just going on what we've seen happen.