Feel free to add them.
To piggy back onto this, if you can provide an official source where Nintendo has revealed them, we will happily add them. Part of the issue lies in that they haven't been officially revealed, and Nintendo has recently taken a strong stance against websites and people releasing information ahead of its wanted time, including taking legal action, which we most definitely do not want.
While it's not explicit confirmation, the latest Japanese guidebook confirmed there was 721 Pokémon in the National Dex, places for the three event Pokémon.
And GTS confirms them, but good point about Nintendo taking legal action.
GTS confirms the names, the guidebook confirms the numbers, but nothing confirms the images. I do think we've gotten enough shots of them here and there (I've seen multiple of Diancie and Volcanion, at least) to make them highly plausible, but if Bulbapedia wants hard info only, those can't be considered. Not to mention he have no supporting info at all (no stats, no confirmed types, etc).
As stated earlier, Nintendo has been getting more sensitive towards leaked information, hence the shutdowns when BW2 came out in Japan, so to appease the Copyright Nazis it's going to be a while before pages for them come up, with the page for Diancie probably coming up around June-July 2014 when Movie 17 comes out, but Volcanion and Hoopa will have to wait until 2015 and 2016 (by which time the fandom is more focused on RS remakes or Gen 7). Despite that, Pokejungle and Serebii have posted the news about the three Pokemon and Mega Latios/Latias, and Nintendo hasn't lashed out at them at all, not to mention only their appearance and typings are known, we don't know their stats, their Pokedex entries, or anything else about them, and probably won't for some time...
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I understand the several reasons why there isn't articles though, the fact we haven't got anything really on them other than there names, potential types and potential images of them (While they are likely, only the former is confirmed of all three) so really all the articles would say is these are Pokémon in the games but we have nothing else about them.
If you guys are gonna be so obsessed with being "official" then maybe you should take down all of your fandom based pages.
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