Simple after 2 years offer a new contract thus making sure his resale value stays high if he does go. We paid decent money for him and if we lost him now we wouldn't get that back. Considering how stingy we are with money that isn't a good thing, the more money we hold onto the more likely we are to spend some of it.
Err, wasn't that exactly what happened? I seem to recall the reports about his contract started at the start of last season, which was the start of his 3rd season at Arsenal.
While all answers are responses, not all responses are answers.