I thing the usefulness will be enormous, but only in the very long term. Remember, Faraday was asked the same questions about his work on electricity. Obviously the big thing the Higgs is giving us is clues towards a theory of quantum gravity. We don't and can't know how useful that would be, but you only have to look to the last unification (QM) to see the potential. Perhaps my answer is "something that is to quantum computers as quantum computers are to regular computers", but we haven't even built a useful quantum computer yet. At the same time, transistor design for "regular" computers relies heavily on QM. So perhaps a better answer is "something that is to today's computers as today's computers are to things that were around in the '20s". But what that is, we can't even imagine - if we knew what the theory would look like, we wouldn't have to discover it.