Even the latest Iphone is inferior in maany ways to Xbox 360. Now with the economy slowing and node shrinking slowing no way. People who say well get PS4 level level performance are ignorant.
IMO, it isn't an arguement how "powerful" mobile devices get. It's convinience. Tablets, smartphones - they are not being bought as gaming devices. They are being bought as convinience, lifestyle, to a certain degree media and socialy integrated and connected hi-tech devices. Sure, just because of that 1 billion market, a large percentage happen to have downloaded Angry Birds or some other simplistic game, doesn't make those people "gamers".
And just because there are overlapping markets of probably the majority of current console owners who also happen to own a tablet and occasionaly do game on that device, does not mean they would give one up for the other. A consoles advantage is not necessarely the technical superiority, but it offering a convinient way to its buyers to play video games in the livingroom on the big screen, offlien and online with a dedicated controller and be immersed or entertained in a way that is not possible on a mobile device.
Sure, the Vita and its successors might be losing their ground because mobile devices are catching up and ultimately there will be less of a point to get a dedicated mobile gaming device, if the experience on a smartphone or tablet can get close to it. That's precisely why Sony is integrating Vita into their PS4 strategy and offering something that's unique. Sooner or later though, I expect them to give that up in favour of an Android/iOS app and offer that kind of connectivity with their future console (perhaps PS5?).
But consoles being breached by cellphones? Not seeing it. The only thing I see happening is less casuals that were suckered into buying a console for their mainly very occasional gaming habbits. They are the ones that might have bought a console in the past and only got a single game, if even that - and the device mainly sitting there collecting dust. These people effectively are better off getting a hi-tech smartphone or tablet to download the occasional mini game. This will have an impact on console sales, but not necessarely software sales - and that's where all the big profits and revenues are made.
Also as another point: Most games on smartphone devices are quite cheap. As technology moves forward and games become more complex, so will development costs. To really match it up with the console games, games on mobile devices will become increasingly expensive. Even if on a technical level it were possible to create a game such as CoD on the tablet, I definately would not chose to play it on that device over my livingroom set-up on a console.