It's already dead
In a few years the handheld market will barely exist, solely occupied by a cheap, first party supported only Nintendo / Pokemon device . I don't see Sony doing another handheld after PS Vita. And no publisher in their right mind will support a portable console.
The world has changed. Tablets have taken over the portable console use case. With games like Walking Dead, TWAU, Clash of Clans, Best Fiends, Vain Glory, Banner Saga and Spy Master tablet gaming is finally much more exciting than portables are, even for a more demanding gamer like myself. Add to that the ability to have all your games one touch away, integrated social networking, lower cost of games, bigger screens, better graphics... Tablet gaming is bound to flourish.
Like many gamers I will miss console style controls on the go, but something has to give.