Regardless, low number of powerful cores is suitable for TODAY's workloads. Be it 2 or 4, it makes little difference. They are there to support today's iconized UIs and windowed workspaces.
Future UIs may not be equal and software solutions to support them may be different, more or less parallelizable. Saying that two cores are enough for all time is ridiculous, to say the least.
It seems that both Sony and MS have decided that more weaker cores (with more powerful graphics) is suitable for today's console generation. Latest gen handheld flagships pretty much all have 4 cores. Software WILL adapt to resources offered, sooner or later. It doesn't really matter if it's only marketing or something more, they are here to stay and they are what SW guys have to work with.