Close - It will update to "Yup." The source code reads:

    if (!(typeof worldHasEnded == "undefined")) {
        document.write("YUP.");
    } else {
        document.write("NOPE.");
    }

And, it even comes with a warranty:

> <!-- if the lhc actually destroys the earth & this page isn't yet updated please email mike@frantic.org to receive a full refund -->