[Newsday] What a difference a year makes. In 1997, the Republican-led Congress was celebrating passage of legislation to expand options for private plans to participate in the Medicare program. The goal was to have elderly and disabled beneficiaries increasingly choose to enroll in private plans instead of the traditional fee-for-service part of the program. While it is premature to pronounce a trend, tens of thousands of beneficiaries will have to change HMOs or return to traditional Medicare. Moreover, the major trade association representing HMOs is calling for permission to raise premiums or cut benefits - or else. What does this all mean?