President Donald Trump offered corporate America a sweeping tax vision whose ultimate promise of lower rates and more global competitiveness depends on one thing: longevity. Given the plan's uncertain costs, longevity may be one thing the proposal can't deliver.

The tax plan released Wednesday by top economic adviser Gary Cohn and Treasury Secretary Steven Mnuchin provided much for multinational corporations to rejoice over — it calls for slashing the corporate income tax rate to 15% from 35% and applying a one-time, low rate to an estimated $2.6 trillion in offshore profits that have so far avoided U.S. taxes.

The plan also calls for shifting to a territorial system for corporate taxes in which, going forward, most foreign profits would be exempt from U.S. levies. Currently, the U.S. taxes corporate income no matter where it's earned.