There was a time when this question didn't involve a huge amount of games.
But if you look at the confirmed list of titles for next-generation consoles, you see a lot of open-world titles. Perhaps it isn't surprising to see developers taking advantage of the extra power in this fashion- larger, more dynamic, more realistic virtual worlds. I have a bad feeling that the days of true linear adventures are numbered, but that's another topic for another time.
For now, let's focus on your most-wanted open-ended, freedom-based next-gen game. At first, I probably would've said inFamous: Second Son , only because I adored the first two games and I'm about 99.4% certain I'll adore the third. But the more I see and hear about The Witcher 3: Wild Hunt , the more excited I become. Granted, there's more in the way of doubt (I'm not familiar with the series) but if CD Projekt RED can pull off what they claim, it'll be absolutely mind-blowing . I mean, we're talking about a title that has the chance to be evolutionary, if not revolutionary.
Then again, there are plenty contenders out there. Destiny is gonna be catnip for the shooter fans, for instance, and Assassin's Creed IV: Black Flag is a definite possibility. Watch Dogs is another one, although it may not be quite as open-ended as other games on the list. Is there one I haven't mentioned that sits atop your priority list? Of course, you could just point to Grand Theft Auto V and be done with it, but that'd be cheating. It isn't set for next-gen consoles…at least, not yet.