Would it be possible to design a SoC have to two antenna?
I believe that's default. All cores share resources (IO being one of them). Each of the cores wouldn't have their own antenna though, no. Wifi/Cell/GPS/Bluetooth may have their own antenna though. There's no point in duplicate antenna for two different applications because one would cause so much noise on the other one that you'd never be able to receive anything besides what the other antenna is broadcasting. 

Instead, the standard way to do multiple things on an antenna is to do TDM (Time division multiplexing).