Right now gold backed debit cards are a gimmick.
The next stage will be a fad if they catch on. I don't like astronomical fantasy projections so it's up to each individual to decide what a fad is worth. Then they could always revaluate what gold's best use would be in the world economies of today. Transparency is a good word. Gold would certainly be able to help with that. Gold would also be an excellent insurance premium. Economically it makes no sense to back up a currency with 100% gold but there is a case to be made for a 5% backing in a lot of situations. Ironically a perfect world is not an all or nothing scenario.