King Felix and Kershaw have a shot if they stay healthy and play long enough.
King Felix will have to have a couple of 20 win years in the next few seasons to get to 300.
He's at 134 right now, let's give him 13 more for balance of 2015.
That'll put him at 147 wins 11 years in.
Should he play 9 more seasons (he's signed for 4 more years after this year) he projects at 267 wins, based on his present win rate.
Kershaw is in his 8th season, he's at 103 right now, lets give him 10 more wins this season, he'd be at 113.
Should he play 12 more seasons, he projects at 283 wins, based on his present win rate.
Presuming good health for both pitchers, I'd put my money on Kershaw rather than Hernandez.
An aside, Kershaw's salary for the next 6 years: $32,571/$34.571/$35.571/$35.571/$34.571/$35.571 (thru 2020)
And Hernandez's salary for the next 5 seasons: $24,857/$25.857/$26.857/$26.857/$27.857 (thru 2019)