Based on Jones' injury record at previous training camps, I wouldn't assume that anyone is not going until the tournament starts.
If Youngs doesn't recover or gets crocked in the training camp, Care is gonna end up going.
If one of Shields/Wilson gets injured in training, assuming he's not already going, Robshaw is gonna end up going.
Brown should go anyway, if Jones isn't utterly insane, at least as FB back up, but if Daly or Nowell are injured by the time the team leave the UK then Brown will end up going.
If Mako is confirmed out, I wouldn't be surprised if they beg Marler to return.
We will not be seeing EJ's first choice world cup squad in Japan because there will be injuries