(The Wall Street Journal) – Consumers could see some immediate gains from health-overhaul legislation in Congress. But most benefits would take years to kick in.

The impact of the health bill hangs on how the final version is written, and lawmakers will have to merge the Senate and House bills. Democrats still face fierce Republican opposition, and they don’t agree among themselves on controversial issues such as a government-run insurance plan.

Still, here are some likely changes to expect.

Beginning next year, Medicare beneficiaries would receive a 50% discount on brand-name drugs when they fall into the coverage gap known as the doughnut hole, according to an analysis of the House and Senate legislation by consulting firm Avalere Health.

Both bills also would eliminate co-payments for Medicare beneficiaries when they receive preventive services, such as cancer screenings. The proposal, which would take effect in 2011, could prompt private insurers to follow suit, says Dan Mendelson, president of Avalere.

In addition, consumers could see tighter insurance regulation. Starting in 2010, health insurers wouldn’t be able to impose lifetime limits on coverage or retroactively cancel policies — except in cases of fraud — after patients fall ill, according to the Avalere analysis.

The legislation would affect different groups differently. Many of the 10 million enrollees in Medicare’s private insurance plans, for example, could lose some benefits under proposals to cut payments to those plans beginning in 2011. Among the targets: free dental and vision coverage, which aren’t covered by traditional Medicare.

A few years later, most consumers would be forced to buy insurance or pay a penalty, and some higher earners or generous plans could be slapped with more taxes. One proposal, for example, would add a 0.9% tax on individuals earning more than $200,000 a year. Young people also could end up paying more for insurance.

The biggest winners: Some 30 million uninsured Americans that the legislation aims to cover, especially lower-income individuals who aren’t yet eligible for Medicaid, the state-federal health insurance program for the poor. But that expansion is at least three years away.

Patients earning 133% of the federal poverty level — $10,830 for an individual in 2009 — would be eligible for Medicaid in 2014 under the Senate bill. The House bill, which is more generous, would push it to 2013 and expand Medicaid coverage to those earning 150% of the poverty level.

Under the same timetable, many more people would receive government subsidies to buy insurance. The subsidies for premiums and cost sharing would be doled out based on a sliding scale and stop at people earning four times the federal poverty level.

Beginning in 2013 under the House bill and 2014 under the Senate version, insurers would be barred from denying coverage based on a patient’s health status or pre-existing conditions.

Insurance companies, meanwhile, would have to follow new requirements to help consumers contain out-of-pocket costs. The maximum out-of-pocket costs would be $5,000 for an individual under the House bill, and $5,950 under the Senate bill.