There have been lots of mentions of those involved in the show saying maybe we had already met RJ after season 3 and/or others. It is entirely possible that this was said back then because they hadn't even decided who RJ was at the time. And perhaps they still haven't decided who RJ will turn out to be - either because they just haven't or don't want to make the decision until next season to keep it secret or because they are going to seek some viewer input. CBS did make history earlier this year on Hawaii Five-0 by having three alternate endings based on the three suspects and letting the viewers vote during the commercial break.