Basically, it's a good step going forward. However, it's more harmful to get a new electric vehicle before your old vehicle has essentially broken down. The carbon emissions from running a very fuel-inefficient car dwarf the emissions from making an entirely new car. Basically, we need to maximize the usage of the current inefficient vehicles and then we should move on to the electric cars.

Essentially, like with any utility item. Use the current one to its maximum and then once it's time to move on, then get the new and shiny one.

The answer is yes, they will.

Basically we will use less energy (like 1/4) (and money) to run these cars. Plus we can use renewable energy directly to power them. City wise, the huge benefic will be the air quality, reducing pulmonary diseases (and others).

Replacing all the ICE cars with electric ones is a huge undertaking and basically mission impossible in the near future, due to the production rate. But replacying engines in today's cars is a very good idea. because we dont need to fabricate a new car altogether, basically only the battery and electric engine and stuck them in the old body shell.

If anyone is interested in this subject, you should search for "transport & environment" and "electrek" websites, which contains good articles on this.

Absolutely they will, yes. Our reliance on fossil fuel is one of the biggest obstacles that our world faces in terms of the environment, and if heavily reducing or completely removing it out of at least a big chunk of our resource usage will hopefully contribute to an eventual elimination of fossil fuel being used.

i do believe because electric / hybrid cars have better efficiency.

I don't believe the change to electric vehicles, or electric anything will be directly what saves the world, even though of course less waste product will help in the long run.
But in the short run they will actually be worse, as manufacturing processes (all the way from raw materials to final products and shipments) will have a huge impact on replacing all present systems. And the power has to come from somewhere, and at present that somewhere is mostly going to be imported coal power, or something just as potentially bad for our planet.

However, I think the shift to electrical systems will make focus shift over from oil/coal to how to produce cleaner energy in the amounts necessary, and when that focus shifts for real we usually make huge strides forward. And since cars are really the first step where switch to electric will have a huge impact both on environment and on existing power plants, it might just be the catalyst we need to get that shift of focus from the big players. And once the power is produced clean, with present systems drawbacks long gone - then electric propulsion will be very clean indeed. But it will not be the saviour on it's own.

Yes, but currently no. By having more electric vehicles right now, we are actually increasing emissions, due to all of the emissions from creating the batteries using the current methods. However, by buying such vehicles right now, we are also showing car manufacturers that these vehicles are the future and thus they are investing more money into such technologies which combined with other more greenier forms of creating electricity will result in a better future.

To prove why it is so important to prove the consume desire for such technologies, look at how hydrogen vehicles were developed and them flamed out, since the technologies, infrastructure, and then end product (the car) all were funded enough and then were basically obsoleted by electric vehicles. (However, with better hydrogen production and storage technologies, this could change, but more money is being spent towards electric vehicles than hydrogen vehicles.)

People need to keep in mind that electricity is currently produced, in its majority, from non-renewable energy sources as well.

Until that is tackled, no, it's not an actual improvement and some studies have actually shown that the emissions may be worse in the long term.
Therefore, using electric vehicles is just like hiding the ashes under the carpet.

thx