CNG vehicles would remain a preferred mode of transport in and around city area due to presence of CNG filling stations.
But for long haul trucks and buses , LNG would be preferred as LNG in liquid form can be stored in Cryogenic fuel tanks for long distance journey and no top up required up to 1000-1500 kms and even more .
But both CNG & LPG are non-renewable energy , though both are 8-16 times cleaner than petrol diesel vehicles in terms of carbon. Further , we have to meet our CNG/ LNG requirement partly through imports.
Therefore , CNG & LNG are approaching towards semi-final. and both would gradually & ultimately be replaced by renewable energy like CBG (compressed Bio gas) & LBG (Liquified Bio gas).
The beauty of the technology is such that the existing CNG network/ Infrastructure can handle CBG / LBG fuel dispensing and existing CNG/ LNG vehicles will be able to run with CBG & LBG fuel. After all all the four contain a simple molecule called Methane CH4 as source of energy.
The other alternatives would coexists together for quite some time - EV, Hybrids , Ethanol , Ethanol + petrol, Bio diesel , Hydrogen IC and Hydrogen fuel cell.