http://planetside.station.sony.com/images/features/devuplink/73007/2_legal.wmv
Both teasers are from SOE, they just got hosted on Youtube, people complained enough that SOE decided to host the high def version themselves (that's what you see here). It's a windows media player file that might not play upon opening the link, just press play on the player again to start it.
As with the first one, don't blink or you'll miss it, also crank the sound cause there is 3 words spoken in the very beginning but they are really soft.
Lots of theories flying around Forumside and but nothing with any subsistence. In my opinion this is exactly what SOE wanted to happen and why the vids are so short and no real information in them.
This has been analyzed on over 37 pages of forumside in two days.
Some concrete/significant things from the video.
1. This video was shot in the basement (under the spawn room) of a LLU Biolab.
2. It was filmed from the middle tube of the room, which currently there is no person in any of the LLU Biolabs middle tubes.
3. The character walking seems to be a female NC rexo armor with a JH and Deci. The coloring of the armor is off, maybe because of the green liquid that is in the tanks.
Some theories from forums.
1. A playable fourth empire (maybe Vanu or the original terran republic (this one seems unlikely))
2. A permanent NPC fourth empire.
3. A temporary NPC fourth empire that brings new technology to the game and then is beaten back by the three empires.
4. The tube people are finally waking up. Laugh cause this one is supposed to be funny.
Additional theories not related to video.
1. New base layouts (yeah right)
2. Bringing reserves back
3. Unbending and/or new bending type event
4. Additional BR and/or CR caps.
If you want to look through it yourself http://forums.station.sony.com/ps/posts/list.m?&topic_id=88000011784
I actually only looked at about 10 pages so there may be more important stuff in there.