Of course premiums are going to fall. Simple economics. More people buying into the risk pool = more risk being spread across a larger body of participants = reduced costs for each participant. Only someone not familiar with insurance risk would argue otherwise.
Here's the question that needs to be asked: How has access to healthcare been affected? Not theoretical access, such as those who have insurance and now have the ability to have their procedures paid for by an insurance company. But rather ACTUAL access, such as their ability to make an appointment and actually be seen by a physician who accepts their insurance? We've increased the number of participants, yet the pool of physicians has not grown. Furthermore, more physicians every day are refusing to contract with certain insurance companies because reimbursements, which are tied to Medicare/Medicaid tables, are horrible (and getting worse).