Whither 4G?

Last week, in class, there was a question about what 4G will be. My answer was - as of now, 4G is in the speculative phase and there isn't really anything concrete as to what 4G will be. Here is an article that has been recently published about how the air interface of cellular systems will likely evolve into 4G. As discussed in class, they only speak of the enabling technologies and architectures - such as MIMO, OFDM, integration of cellular and local wireless networks and so on. It has a good overview of the different generations of cellular systems as well.