Technically they already have ditched Symbian considering how they outsourced Symbian to Accenture which means they don't make it anymore. And since they no longer make Symbian phones, it does pretty much show the end of Symbian. I mean, last few updates were mainly just fixes and improvements.
It's said that Nokia is working on an entirely new OS in case Windows Phone fails based on rumours that is. But I doubt that, the way Elop is going. Getting another platform on to their devices are more likely to happen though.