Last generarion we saw the biggest spike in sales that we are ever going to see, so it is safe to say that this generation will have totals that are considerably less
As for the PS4, it is pacing a bit below the Wii did, and will probably last on the market for about 6 years. The peak year for this system will be 2016. Do math and extrapolate numbers, and you will get something that is around 80M units.
As far as Wii U is concerned, I think people are really starting to see the magic. With Splatoon and Super Mario Maker exceeding people's expectations, I think we are likely to see a pretty big spike next year, and when it's all said and done, this console will top out somewhere between 50 and 55 million units sold. 2017 will be it's peak year.
Xbox one has the roughest go of things though, unfortunately. With the rising popularity of tablets and idevices, people aren't really going to see the need or appeal for Xbox one. Football season is starting, and everybody can already watch football on their smartphones, so this system is really only going to appeal to the dedicated fans who want to watch football AND play halo.
I'm a damn good market analyst if I don't say so myself