Nice idea, trouble is someone has forgotten the price of land that has planning permission and that a garden city by its very nature will have a lot of open space. I also think there are targets for housing density still.
So the development will have loads of flats and no matter what planners might say people still want a house.
Potentially the houses are going to be too expensive, unless the council owns a lot of land and effectively gives it away, or house builders start building townhouses to gain the maximum utility from the land they can build on.
The devil will be in the detail, will they plan for the future around the needs of young families (or those wanting to start families) or those who are 50+ and whose children are flying the nest (and hence make an easy profit)?