I lied earlier, but this time I really mean it's the last I'll say
It is unknown if the long-term costs will be greater or lesser than what they would be without this thing. The CBO estimates there will be long-term savings, but that is taking the assumptions built within the bill at face value.
Health care in this country needs to be reformed, because without that, costs definitely are going to go to high too quickly--to the point where many of us who currently are happy with the status quo won't be so happy anymore. But the ACA is a mixed bag of savings and expenditures, and the potential ramifications of the insurance exchanges, the low-income subsidies, the Medicaid expansion, and the individual mandate generally are too complex to accurately estimate IMO.