Not a very good comparison I'm afraid, Sears didn't lose to an other company who was offering the same service, they lost to a series of companies that offered

Not a very good comparison I'm afraid, Sears didn't lose to an other company who was offering the same service, they lost to a series of companies that offered the same utility but in a very different way. DDG is mostly just offering the same service as Google (really, only a fraction of the service because Google is a lot more than Search these days). As such I expect that at this point if a Google-killer appears it's also be a DDG killer as collateral damage.