Hospital and health plan leaders talk in almost apocalyptic terms about what might lie ahead if Republicans abolish Obamacare without a blueprint for its replacement.Their doomsday scenario: Millions of people could lose their health care coverage, hospitals could hemorrhage cash and shocks to the $3 trillion-a-year health system could send ripples through the entire economy.“That transition period is going to be like that slow-moving tsunami that we know is coming, and we can watch it and try to prepare for it — but in the aftermath of the tsunami, there’s devastating loss that we never could have planned for,” said Heidi Gartland, vice president for community affairs and government relations at Cleveland-based University Hospitals Health System.