It's really impossible to predict. At this point, it's not so much seats sold, but how many seats IM thinks will be sold. With a Q fare you should have a decent chance - ahead of all the Ws - but many of us have watched empty J cabins fill completely while our upgrades die on the waitlist. That's why you'll often read that the only sure way to upgrade with a GPU is to search for R and confirm at booking. Anything else, and you're just buying a ticket in the GPU lottery.