Thing is, until we know what the OU environment will look like, it's impossible to tell whether or not something will be OU. We can speculate on movesets that would do well in the current metagame, but we have no way of telling whether or not it would work well when October has arrived (or more likely, January, when things have settled). Even if all stats and the entire movepool of a new 'mon was released, we have no way to know if it will really be that good when all new stuff is implemented.
Perhaps we get to know about, say, a Qwilfish evolution that would flatten any- and everything in the current OU, and which would get the boot to Ubers within days of being introduced to the BW2 metagame. Everybody playtests it and decides that "This is awesome!!!" and "Can't wait to use it in-game!" and such, but when October comes we find out that the Pokémon is completely screwed over and/or countered by new Pokémon, moves or mechanics.
I've used the analogy of Beedrill earlier, and I'll do it again: Imagine taking a Beedrill fresh from BW2, and send it back to the GSC era. It has moves like Drill Run, Toxic Spikes, Brick Break, X-Scissor and other stuff that was completely unheard of at the time. Even its ability would be unique (seeing as nobody else would have abilities at the time). Beedrill would be a staple on any GSC team.
Yet Beedrill has always been Beedrill: terribad. Without lucky matchups/dumb opponents, it will be squashed like a bug in most battles. From a GSC point of view, its moves are totally awesome, metagame-changing, ban-worthy powerful. But here we are, and Beedrill is in NU, and even there it seldom sees action. Because even though as amazing those moves are, everything around it has been treated just as well or (in most cases) even better.
A more recent example: Techician Breloom. Sure to change the metagame, huh? People were posting those awesome damage calculations, theorizing that Scizor would finally meet its match. Well, so much new stuff was released at the same time that Techiloom kinda vanished in the crowd. Yes, he's awesome, and he does exactly what he was supposed to do. But he doesn't stand out as the champ we expected, just because the conditions of the metagame changed.
Oh, rambling now. Anyway, what defines an OU 'mon isn't something you can predict before the paradigm shift happens. We can wish for "This or that to be OU-worthy", but we don't even know what "OU-worthy" even means at this point. Perhaps Chip Away will become the next Outrage or Close Combat, because everything gets Defense boosts from the inner circles of hell. Perhaps it will be a stallfest because GameFreak imposes a hard-coded limit of turns in a match. Perhaps we won't even be able to assemble a proper metagame, because everything gets so overpowered or random that it's impossible to play competitively. We don't know. But it will be interesting, that's for sure.