The Honda City as we know it, and called the Grace is some markets already comes with a hybrid engine option. But not in India. However, Honda is planning to introduce such technology on their popular sedan. However, to keep costs under check, considering the Honda City is already overpriced, Honda will work on a mild-hybrid technology similar to the Maruti Suzuki Ciaz.
Honda is going to launch an all-new model of the City by 2020. And when this happens, the new City will come with the mild-hybrid technology. Although Honda has the technology of a full hybrid system for the City / Grace, it won’t come to India. Honda has already decided on this.
On the Maruti Suzuki Ciaz, the SHVS hybrid tech works in a way where the regenerated batter helps provide a boost to the engine certain situations reducing the fuel consumption. So although the petrol / diesel motor keeps running all the time, the hybrid tech assists in a torque boost reducing the load on the motor. There is no pure EV (electric) mode in such a setup. Honda will most probably have a similar setup on the new City 2020 onwards.
But, it is unclear of both petrol and diesel variants of the City will come with this mild hybrid technology.