It's worth revisiting this post on the generational stability and turnover of US Presidents. Members of the Silent Generation have been presidential candidates since Mondale in '84, but have never won the election.
Generational membership does not wander around either -- there are long blocks of between 28 to 32 years that belong to one generation, then it switches to another generation for another long block. Not every generation has its day in the White House sun, however, as though it were a simple progression from one to the next. Time and again throughout American history, the presidency skips over entire 20-year birth cohorts, the latest of whom are the Silents (born roughly from 1925 to 1944).
On the Democratic side today, both Bernie Sanders ('41) and Joe Biden ('42) are Silents. Given the track record so far, neither would win the election if they were their party's nominee. Hillary Clinton is a Boomer ('47), and would not be out of generational place if she won, continuing the current unbroken string of Boomer presidents beginning with her husband back in '92.
The front-runner for the Republicans, Donald Fucking Trump, is also a Boomer ('46) and would fit right in with the ongoing reign of Boomers. Most of the other candidates are Boomers, too, except for Gen X-ers Ted Cruz ('70) and lightweight Senator Marco Rubio ('71).
Neither one stands a decent chance at getting the nomination, so 2016 will not be the turnover year when Gen X begins its long presidential reign. And given the trend toward incumbency in political office since roughly 1980, the soonest the turnover could happen is 2024.
After that, the Millennials will be the next generation to be skipped over for presidency, when the torch will pass to whatever this post-Millennial generation of children today will be called.
I'm really hoping Sanders gets the nomination, not only because it would serve as a populist victory over the elitists within the liberal wing, but because it would hand the election to the populist candidate in the conservative wing, who is a Boomer rather than a Silent. I'd take a Biden nom next, since he too is a Silent but wouldn't send a populist signal to the elites.
Realistically, though, it will probably be a Boomer vs. Boomer showdown, with generation playing no role in the outcome.