I totally agree, with what you are saying. I'm hoping that the artist renderings are made to show what everything looks like, but once people get on that there will actually be solid doors on the toilet part and the shower will not be see through.
One interesting story on the threat that I mentioned in my earlier post, someone posted that they were on an NCL ship (can't remember which one) and if they opened the bathroom door right after a shower the steam would set off the smoke alarms and a team of security people would come running to see if everything was okay. I hope that doesn't happen with the new setup on the Epic. A lot of security will be getting to know the passengers way too much.
I guess the best bet is to make sure the bolt is used on the door and to hang the do not disturb sign. If you are rooming with people you don't want to have them get to know you that well, you'll need to arrange "shower" times or some kind of signal so that they know not to walk in at the wrong moment. Though I'm hoping that the privacy curtain will wrap all the way around so that if someone does walk in they won't get an eyefull.