When Europe's population would go down (as current trends persist) and when Europe would manage to throw out the immigrants the time would be there to restructure our cities big time as a lot of the projects from the 19th century and the 20th's are on the verge of falling apart.
Still..people will have to be housed and not everyone can afford a villa or a luxurious condo eventhough prices will drop sharply because of the lower population pressure. So: this is were social housing comes in and it would be a good idea to take a good look at the ideas of the garden city movement and create humane neighbourhoods ,by mixing areas with a higher density with areas with a lower density, and with plenty of space for people to live, have a nice garden to maybe grow some food, plenty of space for children to play and communal facilities like a small community centre with a community school, a nursery, shops, a small medical centre, a community park/pond, a library and a small sports centre. And where possible (if close to a railroad) the community centre can be integrated into a railway station and a bus station. And if you really want to try to keep it local: provide some plots for some small-scaled office space.
Of course it would be nice to use more traditional architecture and mix it with some more modern ideas but one has to use a human scale and to let the area blend in with nature.
Something like this would definetely be nice in some areas in Northern Europe: