I am not sure anyone really knows how this is going to turn out. These programs historically have always been much more expensive than anticipated. Projections for Medicaid spending when the program started were a faction of the actual costs we are seeing now. One big reason is because life expectancy has increased since the time Medicaid was enacted.
Obamacare is a 2700 page legislation. There are numerous taxes and regulations in the bill. The thing that holds it all together however is the individual mandate which has now been declared a tax by the supreme court. This will require everyone to purchase insurance or pay a penalty. This will help to absorb some of the costs.
There are also 500 billion dollars in Medicaid/Medicare cuts that have been set aside to pay for some of the other expenses involved with Obamacare. Eventually the states will also have to contribute to covering many of those who are not currently ensured that will be added to government insurance programs. For the first several years the federal government pays for the increase in the number of people insured by the government programs. This responsibility will shift to the states over time.
No matter how you look at it, this program will expand coverage but not without additional cost. Increasing taxes or cutting spending in some other programs will be necessary going forward to maintain what amounts to a new entitlement. Insurance premiums have already gone up as a result of the bill and this will also no doubt continue.