22 JUNE 2015
Nothing too shocking here. CCI says clearly, "You'll need your physical Comic-Con 2015 badge to be eligible for 2016 Attendee Preregistration."
Previous attendees already know all about this, but first-timers might have entertained the idea of selling off (or just giving away) their badge on Sunday when they're done with the Con. So - no, you can't do that.
Let's assume from this that we're looking at the same type of Pre-reg and Open Reg we had for this year, without any major changes. Which - as dire as it was in terms of the odds of just getting a badge - did run more or less smoothly.
ETA: Every year people ask, "Why can't I just take a picture of my badge? Why do I have to hang onto it?" So let me address this now. First of all, why screw around with your chances of getting a 2016 badge? Even if taking a picture or just copying down every number on the badge will technically suffice, is it really that burdensome to keep the badge around? I definitely would not give your badge to anyone else. It's just not worth the risk of losing access to SDCC.