What we know so far:
-It will be a brand-new animated show, NOT a rebroadcast of the old show
-It will be a series, not a movie
-It sounds like it will be voiced by the original cast, or at least they want to TRY to (Kotono Mitsuishi and Toru Furuya seem to be confirmed as Usagi and Mamoru again, at least?! This is still a bit unclear.)
-It will have OP and Ending themes by Momoiro Clover Z
-It will be streamed WORLD-WIDE (confirmed by Famitsu Coverage!)
-It is intended to be targeted towards older fans of the original series (though I'm SURE it will draw new viewers, I mean, c'mon)--this doesn't mean it will be "adult/more serious/more violent", however.
-As of right now, the title is just "Bishoujo Senshi Sailor Moon", same as the original series/manga.
I didn't get to watch the entire stream because apparently my computer hates Niconico, but feel free to add anything in the comments or just GENERALLY FREAK OUT BECAUSE I KNOW I AM! *____*
EDIT: There are a LOT of places reporting that "Otome Sensou" is the new OP. This doesn't look to be the case--it's just Momorio Clover Z's newest single that's a theme to one of the new Pokemon movies, and they were promoting it at the event. It is unclear what the new OP will be right now.
EDIT #2: I don't know where people are getting this "IT WILL FOLLOW THE MANGA MORE CLOSELY AND WON'T BE FOR KIDS!!" stuff...just because they said at the event that they wanted to do something for the older fans doesn't mean it will be for "adults", and they never specified on if it was going to be more like the manga or not. (I think some people are just taking the "based on the manga of the same name" information out of context.) Right now there are literally NO DETAILS other than what little is stated above, so don't get over-excited excited yet. XD
EDIT #3: From the looks of Kotono's latest blog post, she definitely wants to be Usagi again--she talks about being "itching" to act again, and that the enemy this time isn't the Dark Kingdom, but her own recklessness. XD Awww.
EDIT #4: Sailormoonlife has translations up for the Famitsu coverage on the story here and here in English for those who don't know Japanese. The Famitsu report confirms the claim of world-wide streaming of the new anime, as well as a new, full-color (?!?!) collector's edition re-release of the manga (along with Sailor V), and memorial re-releases of the anime (a new DVD to be released each month with a different Senshi on the cover) starting in October. They also hint that new merchandise will also be released.