I was at WDW last week and didn't see anything at Port Orleans, Polynesian, Contemporary, or Boardwalk to indicate that there would be a new refillable mug program. Now, if the All-Stars and Caribbean Beach are getting the pilot systems first, then, of course, I wouldn't have seen them. However, at Typhoon Lagoon, there is a system in place for the all-day refillable mug that uses a bar-code scanner at the drink station itself. In fact, while in line at Leaning Palms waiting for my lunch order, I heard a CM tell someone behind me to take the mug right over to the scanner-supplied drink station. If Disney will limit refillable mugs to length-of-stay at the resorts, the system would probably be based on the one at Typhoon Lagoon, rather than making people stand in line at the cashier stations.
Whether or not a person buys a new mug each trip or reuses a mug from a previous trip, having a system that limits the amount of refills to the length of stay may seem unfair. One other way to think about it, though, is to consider that a regular soda is $1.79 to $1.99. Unless a person only has a few Cokes, the refillable mugs still pay for themselves fairly quickly.