A Hyundai Sonata PHEV is coming according to this link which cites a Hyundai press release.
The Sonata Hybrid's battery is 1.6 KWh, which puts it a hair above the Ford C-Max. So, by comparison to the C-Max Energi, I'd expect the PHEV battery to be around 8 KWh.the all-new Sonata Hybrid will be joined next year by a Plug-in Hybrid variant of the Sonata, which will be Hyundai Motor's first Plug-in Hybrid. The company also plans to introduce its first dedicated Hybrid model in the second half next year.
... detailed information of the Plug-in Hybrid version will be also released at the show in Detroit, U.S.