It's just unfortunately very out of date. He says something like, "finding the Higgs-Boson Wil be a task for a different century" or something to that effect.
The actual quote is "whether it actually exists is a matter for 21st century physics," so he was completely correct. It was, indeed, a matter for 21st century physics: the Higgs boson was proven to exist in 2012: about 9 years after the book was published.
Well, you kind of made it sound like he was predicting it wouldn't be found for a century (though I suppose is he'd written the book just 4 years earlier, he'd then be right).
It actually goes into some detail about why the Higgs boson is important, it just says "it hasn't been found yet". If you fill in the epilogue of "the Higgs boson was found in 2012" yourself, those pages are still consistent, correct and useful.
It would really be out of date if the Higgs had been disproved, as it would have two pages of, essentially, a branch predictor failure.