I think we all agree that more and more people will move from rural to urban areas and the cities will not only grow in population but also in size. The infrastructure will have to grow to be able to cope with the influx of people and increased demand on services.
I guess in most developed nations we have the 1.0 Era Digital City which is long way away from the 3.0 Era Smart City.
To be a full fledged 3.0 Smart City, every aspect of our life may need to evolve into "Smart". Anyway, here is the complete presentation:
While IoT would be important, access, big data, applications, etc. all will have a role to play.
If you want to find out more about the Milton Keynes smart city, also see this video on Youtube. There are driverless pods and other autonomous cars which may be considered as initial step towards smart cities, see this interesting video here.
Finally here is the TEDx talk about designing these smart cities for future: