In my experience you'll have no problems at all getting upgrades on any of these routes in August - that is peak holiday season and Y is almost always oversold and business travel is very quiet or non-existent. August is prime opportunity for buy up upgrades, and operational upgrades. If you get in the queue now for mileage or SWU upgrades then I think you'll be 99% certain of getting the upgrade.

With one caveat maybe - if there are two of you on the same reservation then you'll miss the upgrades that come along one at a time. Two individual reservations will increase your chances.