Its constantly evolving. For years cars have been getting bigger and heavier, due to mainly safety devices, and our relentless want for loads of tiny motors to do things like adjust the lumbar, wind down the window or move the wing mirror
The latest generations are starting to share platforms and these are being more refined and saving weight. Lastest TT for example shares the chassis across the VW group, is better and about 50kgs lighter.
The engines are one of the most expensive bits of the car as it is. Would you spend £10k replacing the engine in a 5 year old car? Currently the maths say its daft, its hard to see a way that will change in the future unless the chassis get massively more expensive. Plus the true EVs tend to be built differently with the batteries forming part of the whole, how those are going to be recycled is more the issue to me, replacing them with new will probably cost more than buying a new car, you would have to practically disassemble the car to change the batteries!