Personally, I don't even know why this is even a question. Of course, the Spurs pick up the option. If Ian were 26 and his performance was steady, I could understand the hesitation. However, he's 22 and improving. Has tremedous upside and seemingly works hard.
With Duncan, McDyess and Ratliff all likely gone in 2 years, the Spurs would be big fools to throw away a young, developing big of his skill and potential. As I've said before, young, talented bigs are not growing on trees.
After all, Pop's comments on his practice habits and progress are convincing enough for me to believe that the team will pick up his option. I'd be shocked if they didn't.