I don't want The Shield going after world title gold just yet. I'm not even sure it'll get to that point before the dissension leading to their eventual breakup begins, though debate and disagreement and egos over who gets to be the two world champions might indeed play into their breakup when the time arrives.
It does make me think though, that if the ECW World Title was still around, all three guys could go for the world titles and end up all carrying world championship gold. I like the image of them holding up the WWE/World Heavyweight/ECW Championships in the air simultaneously (in this case, I wouldn't have even bothered having them win the US and Tag Team Titles) but it is not to be.