I've been getting more or less all major WWE game releases within the past five years or so, so to keep that up and whatnot, I'll most likely be getting 2K15 as well. In general, there are plenty of reasons for me to buy it, and in some way, this is one of them.
Been wanting to see free-roaming return to the series for a long, long time, and am sure same could be said for a ton of other people, but it's been confirmed to not be implemented (or so I've heard), sadly, which is sort of disappointing. I suppose one negative side of this is, it might have to have us wait every time we enter a new location, which could ruin momentum when participating in matches and whatnot, but that shouldn't be much big of a deal. It does add more to the fun, doesn't it? If you ask me, this is all that matters.
As far as roster goes, I'm expecting it to be pretty similar as last year's. Alongside, I'm also guessing Adrian Neville, Sami Zayn and Tyler Breeze to be there, as they had already made their RAW debut. One person that I'd personally like to see, however, is Sting. I'm not sure if he's already been confirmed as an in-game character or not, but would be fun if we were able to play as him. If they do include him, I'm very interested to see if they give us any story-line focusing on him or not!