You've said this before, and my reply is the same: don't bet against it. The smart money is to take the long-term deal. Gay will be twenty-eight on Opening Night 2014, which means, chances are, he's only going to get one more big money multi-year deal.
A responsible agent will advise him that it's in his best interests to at least consider opting out of that last year, and signing a 6-yr deal at $14M per, rather than to take the option, risk having a bad year, and having to settle for four years at closer to $10-11M per.