Last day before the big E3 reveal and the SWTOR official twitter/facebook accounts have posted another intriguing image.
Looks like they are pledging their allegiance to the Immortal Emperor perhaps?
There are some speculations on the forums that these lightsabers belongs to various key characters as noted in the picture below.
Image/info credit (Rebel Scum/Koichi/Theho)
Edit: Another image from reader Ben Gimson posted in the comments below.