It's important to note that this is the CiD. The actual rule that comes out when the internal play test is finished and the rules released could be drastically different- which I think they will be. The reason why we haven't seen a "re-roll" damage mechanic in the past is the sheer brokenness and open to abuse it presents. As a matter of fact, we have seen very little re-roll dice mechanic in the game. It's always been a straight up dice modifier, or "roll an extra die and subtract the lowest die roll".
No, I don't think this will make it into the live game. Maybe. Anymore I have no idea. Where this game is headed and what kind of player they want is beyond me.