I don't think there are many changes in FEHB as a result of Obamacare - except for the usual like extending health benefits for adult "children" to 26 years or limiting FSA for OTC drugs (and those changes do not impact retirees generally) . But there could be some future changes in federal retiree health benefits but not probably for several years.
From a FedSmith article dated Aug 5, 2013 entitled "Should Federal Employees Continue to be in the FEHBP?",
Federal employee retirees may also see changes and are more likely to see changes than current federal employees. In the annual “call letter” to insurance carriers for 2014, OPM
wrote: ”OPM is encouraging proposals for pilot programs where participating carriers offer a sub-option for Medicare eligible annuitants as an alternate choice.”
The article was a mish mesh of FEHB, Congress being subject to ObamaCare, whether other federal employees should be included, etc. so was not clear that these proposed pilots are a direct result of the Health Care Reform Act. I just hope that this sub-option would be an alternate choice and not the only choice or a reduction in benefits - I'm seven years away from Medicare but would like to continue my FEHB and purchase a Part B supplement for complete coverage.