According to latest sources India now plans to now reach Mars 
after the recent victory over the Moon mission. And have put up indications to use the innovative Solar sail engines and the Ion Propulsion Engine. So we put a light on the latest revolutionary space technologies to unravel the hidden treasures of the Universe.
We have always seen that the first place where the latest technologies are put to practice is the field of space. So learning from NASA missions or getting encouraged from them Indian Space Scientists have given possible hints over the mission to Mars, and that too on a low cost spacecraft that would be propelled by innovative technologies such as Solar Sail engine and Ion
Propulsion Engine.
A space rocket works on the basic principle that it leaves a trail of propellant behind it and the propellant in return push the rocket ahead and pushes the spacecraft ahead, and this process is repeated again and again to make the spacecraft propel forward.
Solar Sail Engine-
While in a Solar Sail Engine the thrust or the push is generated by the photons striking the sail. This is quite small but when collected over a large area provides significant acceleration. And with time this acceleration goes on increasing the velocity of the vehicle to significant levels.
Solar Sail is in phase of testing and research but it has promised good use in the space industry.
So you must be wondering how to navigate using a Solar Sail so changing course can be accomplished in two ways. First, the sail can allow gravity from a nearby mass, such as a star or planet, to alter its direction. Second, the sail can tilt away from the light source. This changes the direction of acceleration because any force applied to a sail’s plane pushes at an angle perpendicular to its surface. Smaller auxiliary vanes can be used to gently pull the main sail into its new position.
It has a lot of limitations as the sail has to be made quite large to produce sufficient acceleration and also there should be a constant source of photons but as propel forward the distance between the source and the sail goes on increasing and decreasing the photon efficiency. But i guess the scientist must be doing something for this
Ion Engine-
An ion engine uses this same principle of propellant and thrust, but the great innovation is in how efficiently this happens. The
gas xenon (which is like helium or neon, but heavier) flows into the ion engine, where it is given an electrical charge. Charged atoms are called ions. As soon as the xenon atoms become xenon ions, they can be pushed around by an electrical voltage. A pair of grids in the ion engine, electrified to almost 1300 volts, accelerates the ions to very high speed and shoots them out of the engine. As the ions race away from the engine, they push back on the spacecraft, propelling it in the opposite direction. [The electricity for this remarkable system can be provided by solar arrays, as on Deep Space 1 and Dawn, or by a nuclear power system, as on Project Prometheus. The principle of operation of the ion engine is the same.]
The xenon ions travel at about 35 kilometers/second (77,000 miles/hour). This is about 10 times faster than the exhaust from conventional rocket engines, so the xenon gives about 10 times as much of a push to the spacecraft as chemical propellants do. That means that it takes only one tenth as much propellant for an ion engine to work as it does for a chemical propulsion system. To accomplish some of the more ambitious and exciting missions in the solar system, we simply cannot build and launch spacecraft large enough to carry the chemical propellants that would be needed for the mission. Ion propulsion is one of the ways to get around this problem.
Now the ion engines use only a very small amount of xenon at a time. That means that the thrust is very very low. If you rest a piece of paper on your hand, the paper pushes on your hand about as hard as the ion engine pushes on the spacecraft! It may take 4 days or more just to use up 1 kilogram (about 2 pounds) of xenon. Unlike chemical engines, which can be operated for minutes, or in extreme cases, for an hour or so, ion engines can be operated for years. The effect of the gentle thrust slowly builds up, eventually attaining speeds far beyond the reach of conventional propellants.
Well what i believe that what we would see in the future will be a hybrid prototype that does 
not rely on just one source of energy, like an hybrid electric car that uses electric fuel cell for propagation at some time and when the battery goes down the car car be propelled by fuel engine (petrol or diesel). Also we have been seeing a lot of innovative engines all we could do is wait and watch.