I'm told this will be the first election ever, where Millennial voters outnumber Baby Boomer voters. Will that have an effect on the election? Maybe! I think the generation gap would be more pronounced, if we had a Millennial candidate.
There has never been a Presidential candidate more recent than the Baby Boomer generation. (All the non-Boomers lost in the primaries this cycle.)
It's possible we'll see the first Generation X candidate will run in 2020, against the reelection of Trump or Clinton. On the other hand, Clinton and Trump are on the older end of their generation. Someone on the younger end of their generation, like President Obama, would be in their early 60's and still make a formidable candidate. So it's possible 2020 will also be Boomer-dominated.
Ronald Reagan was the oldest US President, being age 77 when he left office. If we consider that to be the absolute cutoff age, then 2040 is the last possible election with a Boomer candidate. Then again, life expectancy has increased four years, since Reagan's death, so a President who is in their 80's wouldn't be too far out of the realm of possibility...