I wouldn't be surprised if the window is already closing for this constructed personalities where you can't tell if they are real or not. People get relatively savvy to the nuances of new media fairly quickly (within a few years). Sure there will be notable exceptions but I bet some unspoken norms / rules / clues will develop and be roughly accurate guides as to which dimensions the people they see on their screens are real vs. artificial.
The problem occurs when there's deception about its identity. There will be trust issues in the near future if things like this persist. Then again, would it even matter if some celebrity is a real person in the future?