Paid F demand > artificial F demand (upgrades and FF redemption). Although the business case for offering F as a carrot to drive full fare J traffic (+ SWU) makes sense, the fact is the merger brings more markets to the fold which generate strong F demand. See EWR-BRU/ZRH/GVA, forthcoming IAH-LHR, and other routes where 3-cabin aircraft have replaced 2-cabin (some periodically, like EWR-FCO).

United would be stupid not to move 3-cabin aircraft to those markets. Of course, while transitioning F off historical UA routes may be viewed as yet another egregious affront to UA flyers by CO management intent on ruining the airline, it's really just a publicly-traded corporation allocating its resources in what it believes to be the most profitable manner.