If someone pays millions of dollars to a company that promises to freeze their corpse for 200 years, the company can simply freeze the corpse for a decade or two, take the millions of dollars as dividends and executive bonuses, then declare bankruptcy. The dead can't sue.
It was quite common for rich Victorians to donate their grounds/houses to be used for the public good and still today they are owned by the original trust and money from the trust can only be used in a certain way etc... we have many parks because of this (that otherwise could have been developed to extract money).
Obviously the longer the technology takes to develop, the higher the chance something goes wrong; though the concepts of trusts have existed for some 800 years so if it takes only 200 years, I think your chances are good!
There may be exceptions to the rule against perpetuities for charities, but I don't imagine any sane court would consider keeping a corpse frozen to be a charitable activity.