As of the announcement of the new area, this is honestly pretty much a gamble as to whether or not we get it in the new area.
Mence loses the ability to switch in, Outrage, and probably Dragon Dance. Breloom will probably lose Bullet Seed. Zapdos loses Heat Wave, and there is no guaruntee that future tutors will give it back. Lucario loses Ice Punch, Crunch, Vacuum Wave, and Agility. Ho-oh and Lugia are Ubers, as well as both being possibly released via the current Japanese poll. All of those are all competitively viable anyway, whereas Ditto will continue to suck major balls without Imposter. Though Ditto will not be breedable, gendered Pokemon will probably be male only, and thus will be unable to use Egg moves, in addition to their past Generation tutor moves. While it is true that it could become available in a new area, we have no guaruntee of this, and should TPC have chosen to release Ditto on their own, it would have likely come from either Pleasant Forest or Spooky Manor.
If you're just doing this for your favorite legend or whatever that you don't already have, bear in mind that those have been released in the past and will inevitably be released again in the future, and are easily obtainable via the Trade Forum on Serebii or off Pokecheck, whereas Imposter Ditto has never, ever been released, and may never have the chance to be released again. As we have seen with Azure Flute, just because it could exist does not mean it will. Bear in mind as well that an Imposter Ditto will be infinitely rarer than any of those, anyway, and could probably be traded for multiple legendaries.
If you're voting for something that's already been released via Dream World, such as Torchic or whatever, bear in mind that that is also easily available via the Trade Forum or Pokecheck. There is no need to release it again, even if it was in a different country. Besides, the event will likely make its way overseas at some point.
Also, the vast majority of people want Ditto, and uniting votes behind one thing means that we don't get a repeat of Japan and Korea. It is much better to get something that you may want less than something else than something that is entirely useless.
Katakiri of Smogon said:
...In truth, I want Techniloom but since the majority wants Ditto, I've voted for Ditto 30 times today & will continue to do so every day. Doing the math, by the end of November, I'm going to have voted for Ditto at least 900 times even though I wanted Techniloom.
I've looked around on other forums as well. It's not Breloom they want, it's not Zapdos, it's not Ho-oh, it's Ditto. I'd rather have my votes matter instead of voting for a Pokemon that I know will not win.
Do remember that this is not a lost cause - Korea had Ditto coming in second place.
Next Tuesday, when the results come out, should a non-Ditto, competitively viable/not totally useless Pokemon be leading, votes should be redirected at that Pokemon (though, given the way this is going, this seems unlikely).
For those of you wondering why it is Ditto is being voted for, Will-Powered Spriter has explained it well.
...Ditto's [DW] ability causes it to automatically transform into the opponent as it switches in. This means several things:
It's poor speed and defenses are no longer an issue. It no-longer has to survive one turn in order to transform. DW Ditto's IVs, EVs and nature for 5 of it's stats are irrelevant.
Ditto's ability causes it to mimic the opponents stat boosts. If the opponent has several speed boosts and attack boosts, ditto will copy them, making you perfectly even.
Because it doesn't need to use transform, it can wield a choice scarf. Ditto now functions as the ultimate revenge killer; if your opponent has multiple boosts and takes out your pokemon , you can send in ditto to become the opponents pokemon but faster. You should easily be able to take out their sweeper, and now the opponent must deal with your Ditto.
