In the past 3 decades or so, the winner of the presidential election was someone whose name wasn't floating around this early in the process:
1992: Clinton. He was a nice-looking governor of an unimportant state. Ended up beating the sitting president.
2000: Bush. He was the governor of Texas, but wasn't known as a national figure.
2008: Obama. A first-time senator that came from nowhere and won it all, defeating the well-known Clinton and McCain
2016: Trump. Who would've thought he would win with Jeb, Cruz and Rubio around?
The bottom line-- it's too early to throw names in. And, in my view, it's better for someone not to be tapped as a potential nominee so that he/she will not be subjected to relentless attacks by Republicans over 3 years.