It sunsets by default. Means that Obamas successor gets to renew it by EO, or has to go to Congress to make it permanent.
There’s no way, I think, that a Republican president goes the EO route. Even a Bush or a Christie (God forbid). If there’s a big enough backlash (as I think likely) I don’t see a President Hillary doing it either.
Going the Congressional route will require a 60 vote supermajority in the Senate. With Cruz, Lee, Sessions and now Ernest and the other pro-tea party Class of 2014ers I don’t see that as likely either.
Instead there’ll be the kind of paralytical infighting that has prevented both Obama and before him Bush from getting something through. Which is actually a good thing because the amnesty just expires by default without the ability to blame anyone for actively killing it.