She's not the ONLY playable character, she's the main playable character. Last game Joel was the main playable character. They are just mixing things up a little otherwise it would just be more of the same. Naughty Dog now that, so they've taken another angle. Kudos to them.
When you had to play Ellie in the first game did you suddenly throw down the controller in disgust and take your game back?? I doubt it very much, but If you did then you aren't a real gamer and lover of exceptional story telling.
They said in an interview Ellie is the only playable character. If by the end they decide to include him it will be for a 10% or even less, considering you are most likely also playing as the mother of Ellie (the manly woman in the previous trailer), because they said that the story will have "some time swaps" or something like that, making clear you will play in different time periods. I wanted to play most of the game as Joel, just like in the first part.
For me the core of the franchise was the journey of how Joel from being just a psychopath begins recovering his human nature through the curse of the game; and Ellie was just a tool to make that happen. Ellie was a sidekick and nothing more.
I simply just dont care about the game anymore.