It's all well and good saying that, but what about battery life? My PS Vita will last a few hours playing high quality games but it doesn't really need to be always charged for phone calls, texts and the myriad other features you use a phone for, having PSV play times in a phone would mean you mostly need to have the phone plugged in to a charger which kind of detracts from the "mobile" in the name "mobile phone".
Plus, touch screen controls would be a bit sucky, with a console you never need to look at the controller to push X and then Square, you can feel where they are, with touch screens as a controller you'd be spending a lot more time looking down than you would looking at the TV.
Could they be as powerful though? Maybe, maybe it would be a good thing, cheap as chips GPU processing for laptops would be nice.