Im kind of getting the feeling there may not be a tournament this time around. I mean the backround from what i've seen of the start menu of DOA 5 kinda looks like a war or something is going on.....maybe after Alpha-152 escaped she set out to do what she was created for which is destroy everything in her path. It would be cool if like all the characters kind of joined together to like take her and Donovan down!!!
Simple yet 100% perfectly awesome this is probably the best idea for DOA5's story I've heard yet. I'm not a fan of tournament-based storylines. To add to that, how about other subplots going on between certain characters and everyone having different characters as their final boss? Maybe even, since there's no tournament, at certain points of story mode, your selected character teams up with someone close to their story to take someone or another team of characters on, kinda like an idea taken from Chronicles mode on DOA:D (so it wasnt completely useless, lol).
If there really is a single "winner", then I'd guess maybe it's one of the new characters, or another ninja again, lol. If I had to guess it might be anyone other then that, then so far, I agree with others that it could be Bayman. Either that we'll have to wait till the first major DOA5 tournament to find out.
It's difficult to predict who will actually win DOA5 since the fact that this issue has never been relevant on the previous games. For example, apparently, Zack won DOA3 so he could earn millions from the prize and buy an island. In DOA4 there was never an explicit winner but Tina (maybe) due to, if you remember, she stated on TV (in the Bass cutscene hehe) that if she'd win the tournament, she would become a rockstar, something that eventually, she did. So, who knows? xD
I'm pretty sure that just like with Tekken and some other fighters, not all ending are true, they just show you what would happen if they were the ones to win after you beat the game with them. That's one of the major reasons why the stories in a lot of fighters dont come off too clear. I'd assume that Helena's ending in DOA4 is the most true ending and anyone's ending that relates to her's is also true (Bayman's, Ayane's, Hayate's, Ryu's). It could be also that others are true as well actually, because unlike in Tekken no one's ending in DOA4 really clashes with anyone else's (cant say the same for DOA2 though), even Tina's, cuz maybe (and I bet this is true if I know Tina, lol) she became a rockstar anyways. It's not like she had to win to do that anyways, she probably juse used the tournament for publicity for it.
Sometimes who wins the tournament is also mixed in some ways, like apparently (I got this from doawiki I think, and I think whoever put the info there got it from a mook or something) Kasumi gave her DOA1 winnings to Tina (so maybe Zack got his money the same way in DOA3, I doubt Ayane would take the cash just like Kasumi didnt), and on top of that it seems (cuz of DOA:D) Kasumi also had help beating the final match in that tournament, so who is really considered to be the tournaments winner? Kasumi, Ryu, both? lol