Sorry but I reckon your friend is talking out of his 'arris.

I seriously doubt that any vehicle would need re-powering. A re-map of the ECU should be sufficient for every vehicle that may be affected

Sufficient for what, though? Yes it could be remapped to make the car emit the same lower level of emissions in real life driving as in the static tests - but then it will pull like a pig tied to a shed.

Do you think that VW's sales will be affected much? I understand that many people will have bought a diesel VW, swayed by the engine stats, better mpg, lower road tax, but do the majority of the car buying public really care much about carbon emissions? If they did they would stick to their old car. The environmental impact of building a new car must be greater than the exhaust fumes coming from the car you already own. Think about the mining/manufacture of the metals, all the plastic that goes into it, parts and materials shipped from the other side of the globe.

Yes but most people are thick sheep. They buy into the cynical use of the term "green" by all sorts of businesses. Businesses that promote their green credentials are generally unethical in my opinion.

I see VW sales are reported as down for the last month. Mind Vauxhall sales are down even more. What will interest me is how have sales of Diesel cars gone.
I feel people are starting to rethink the type of vehicle they want to buy.
These Diesel Particulate Filters fitted to the modern diesel, are nothing but a nuisance, Why people who only potter around are sold Diesels amazes me. It is just greed on the part of salesmen, keen to sell whatever.
It is interesting to read that Ford are bringing out Petrol vans in the near future, a sensible move.
The days of the diesel are numbered. They say that Diesel powered vehicles will have to pay a higher London Congestion Charge in the near future and some London Boroughs will make Diesels owners pay a Surcharge on parking fees.
It is said that Londons Oxford St is one of the most polluted roads in the world, due to poor air flow and its almost exclusive use by slow moving Diesel vehicles. Taxis and Buses.
Another interesting point is Frances changing attitude to Diesel vehicles. Renault and Peugeot/Citroen, encouraged in the Sixties by the French government developed very successful small Diesel engines. Over time these caught on, due to fuel economy, DERV was cheaper too and later its claimed environmental benefits. Now after tests where Paris banned cars for several weekends, A ban on diesel cars in Paris is a real possibility.

Cities are starting to ban personal motorvehicles from coming into central parts, Bogota bans all vehicles for 7 hours every single Sunday and national holidays, car free days are springing up everywhere. Oslo is planning to be completely car free, Vaxjo in Sweden wants to be free of fossil fuels by 2030, many towns in Switzerland already have complete bans on motorvehicles.
The UK is so far behind with integrated transport solutions and encouraging cycling/walking never mind better public transport, people are too tied to their cars/fossil fuels and won't change, 30,000 (official though closer to 60k) deaths in the UK due to pollution won't be dropping anytime soon that's for sure
All the while people are getting fatter and putting massive pressure on the NHS/taxpayer.
Something has to change but it won't under the current government nor Labour either.