Whatever they do, a phone with Vita OS won't stand a chance.
First, majority of people need their phone to be dependable and secure, and NOT be a "plaything". An OS that evolved around a game console simply won't be treated seriously by consumers.
Second, Apps from all the major players are required such as google map, gmail, facebook, twitter, flash player, whatsapp, youtube, dropbox, etc... needless to say there's always arm-twisting between these, and other companies, to prevent any new OS from succeeding.
Without a serious image and support from these companies, a phone running on such an OS won't hit a critical mass required to attract app/content developers, and it will flop even harder than Xperia PLAY.
At this time, the next Xperia Play's best OS choice is still Android. But even then, I think Sony really dislike the idea of Playstation ecosystem sitting on top of Android. They may think it changes too fast, too many different hardware, or difficult to control piracy.
So even the best choice is not appealing. So I think Sony won't be putting Playstation content on Smartphones for years yet. And that's a shame because It think that's exactly what we all want happening now.