From this image:
I notice 2 things:
1. Unlike the prs-t1/prs-t2 light cover, I can't find any place to place AAA batteries.
2. The black reader with that black case is placed in an inclined way. This suggests, something on the top back position is supporting the reader with case, which is the light part. This might imply the light is CLIPPED onto the back, either detachable or non-detachable with the case. The other thing is, we don't know what the back of the light clip is, b/c that will tell wether this IS a lighted case or acutally a case with a light clip. Funny thing is, the back of the light case is the only blind spot that left us to wonder.
I cannot convince myself this is actually a light case (like T1/T2 official light case), where I cannot find a spot in the picture that tells me where the light battery is placed in the case. Or maybe sony design team actually did decide to throw a light battery on the back of the case...
Also if you look closely to the red, and white case, look how "clean" their top edge is, can you believe that there will be a light neck coming out of there? This makes me believe that it is a detachable light clip even harder.
My guess is, this is another smoke bomb sony drops on us, making us guessing over wether t3 is front lit or not. However, I will consider myself wrong, if sony dare to show the back of that light case.
SONY, WHY DONT YOU JUST SHOW US THE BACK OF THAT PRS-T3 LIGHT CASE?