According to Shimano's site, DA is still coming with 11T pulleys. However, it would not surprise me in the least if they introduced their "innovative" 13T pulleys and encouraged everyone to replace their "out of date" derailleurs with the newer ones. The only other reason I can think of for using larger pulleys is to use a little more chain w/o increasing cage length. This would be more suitable for MTBs as they typically run a wider range of gears. Who knows what the big S will dream up next to get us to replace gear that doesn't need replacing.

Is it really possible to wear a DA rr. der out? Other than pulleys, I would think they would last damn near forever.