Orton, while the most obvious, is the person who I think will make the biggest splash. He's got good mic skills, he's improved substantially in the ring(when I first looked at him, I was somewhat underwhelmed), and his seven month reign as Intercontinental Champion has really earned his respect from me.
AJ Styles is also another definite one to watch. He's got a great look, he can wrestle with the best of them, and on a side-note, I love his entrance theme.
Shelton is another one. He's got a very bright future ahead of him. I see two or three Intercontinental Title reigns, then a world title run. I don't know why, but I can just see that in Shelton somewhere down the line.
Carlito I also think will be huge one day. I absolutely LOVE Carlito. Because, after all, he spits in the faces of people who don't want to be cool. And, damnit, that's just cool.
One that no one has mentioned is Christopher Daniels. I think Daniels is really going places. Once he gets out of his AMW/Triple X deal, I think he could be huge.