Complete electrification is a rather bad idea. Only routes with sufficient traffic density and major passenger trunk routes have to be electrified. With our current electricity generation capacity and the dependence on thermal power for traction power ( solar and wind power are not suitable for wide scale traction power as of now), diesel traction cannot be abandoned and is still very crucial.
Many routes do not have much traffic density and electrification of these routes ends up in creating more pollution than diesel traction. Alternative fuels like biodiesel can be explored as replacements for petro-diesel to reduce dependency on crude oil.