We finally know what's going on with the ending (I was wondering if they'd replace Negai after Tenkuu no Canaria replaced ALMATERIA). There will indeed be a new ending song for the Tethe'alla Hen of Tales of Symphonia THE ANIMATION.
The new ending will be by...Akiko Shikata. The song will be called 祈りの彼方, which I think is read Inori no Kanata
but not sure since I fail at reading Japanese sometimes.
There's also a new PV with said song playing. Click the second one, the first one is the PV from October with Tenkuu no Canaria playing.
I'll embed a YouTube video once someone uploads it.