Updated: Uncharted 4: A Thief's End Announced For 2015

[Sniper Team 4]

He still has his wedding ring. Which makes me think that Elena has been kidnapped, and Drake needs to find this treasure in order to trade it for her safe return. Otherwise, I cannot think of a good reason for him to get back in the game after everything he went through at the end of the third game.

really? the Uncharted games basically go full circle everytime, he ends up just where he started , hell I bet him and Elana have broken up at the start of this one....cause if your gonna do it three times you might as well demonstrate your lack of "effs" given and do it four...make it a record...

I would agree with you, but for two things. The first is that the tone of Drake's voice and the mood they were going for in this trailer. I got the sense that Drake doesn't want to be doing this. He tries to play it off as no big deal, but his tone switches to that of someone who is tired of this and is being forced into it.
The other reason is that I'm hoping Naughty Dog has better story telling abilities than just recycling the plot of the third game.