+1 Sorry to pop OP's balloon, but as a Plat last year I received zero repeat 0 suite upgrades. Yes they will make sure you don't get the worst of the house, but don't count on much more.

It certainly can't hurt to send a request a few days in advance of your stay. But I don't think the front desk even bothers to look at these when pre-assigning rooms, unless you are some kind of VIP. And Plat isn't one.