Valanciunas: rebounding, defense, and great foul shooting
Ross: defense and 3-point shooting, with great athleticism
Davis: rebounding and defense, again with great athleticism if not size/strength (yet)
DeRozan: mid-range game and ability to get to the line
I feel like any deal for a franchise player would probably have to include deRozan because a) he's under contract at a reasonable rate and b) you're probably going to have to replace some scoring if you're trading an elite player for him, as well as put some asses in the seats. Now you throw in one of the bigs, maybe a pick or another of the 4 above and an expiring deal or one of Amir and Fields depending on need and you've got an excellent package. The only thing missing really is an expiring deal. In fact you could easilly argue that's equal to or better than than teams got for Bynum, or Howard, or Paul, or Williams, or Melo, or any of the other superstars traded in recent memory.
To answer Akasingh, the NBA is an extremely fluid league when it comes to star movement. Look at the Deron Williams trade: nobody even saw that coming. Same with Harden. And with the luxury tax penalties getting progressively more restrictive, you're going to see more and more teams unable or unwilling to pay into the tax. As for which stars might be coming down the pipe, the best bet are those players who would need be eligible to sign an extension in the next 2-3 years. John Wall and Kyrie Irving are two examples of players whose teams haven't done a great job of drafting around them (though Wall would have to develop a lot in order to be worthy of a huge trade package, you might be able to get him for cheap if Washington is convinced he won't re-sign). Love seems to be perpetually unhappy in Minny, nobody knows what's going to happen with Bynum, or Howard if the Lakers end up missing the playoffs, etc etc.
Admittedly most of the players the Raps have a shot at aren't real top-15 type guys (I probably overstepped a bit there, top-25 might be more accurate), or at least won't be when they're acquired. You'd probably have to aim for guys that haven't reached their peak yet but aren't happy with their current situation or need to be dealt because of money issues. I think Harden is the prime example there. There's also the possibility of trading for a very high draft pick if a team is looking at a roster redundancy. The point is, if I'm the GM then I'd rather wait for a superstar than settle for a borderline all-star, especially if it's a borderline all-star that I have to pay like a superstar to keep around.